9th Class Chapter 1 Chemistry Short Questions

Question: 1

Give the composition of Earth Crust with respect to three major elements.

Answer: 1

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Earth Crust is formed by three major elements having following percentages. Oxygen 47% Silicon 28% Aluminum 7.8%

Question: 2

Define Empirical formula and give examples.

Answer: 2

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"It is the simplest whole number ratio of atoms present in a compound" Example: Empirical formula of benzene(C6H6) is CH Empirical formula of Hydrogen peroxide (H2O2) is HO

Question: 3

How can you justify that air is a homogeneous mixture. Identify substances present in it?

Answer: 3

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Air is a mixture formed by be the physical mixture of the substances like nitrogen, oxygen, carbon dioxide, noble gases and moisture and it has same composition throughout. So,it is homogenous mixture.

Question: 4

Which term is used to represent the mass of 1 mole of molecules of a substance?

Answer: 4

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Gram molecular mass

Question: 5

Difference between homogeneous and heterogeneous mixture.

Answer: 5

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Homogeneous mixture: Mixtures that have uniform composition throughout are called homogeneous mixtures.

example: Milm, Brass, Ice-cream.

Question: 6

What is the application of Inorganic Chemistry?

Answer: 6

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It has application in every aspect of chemical industry such as glass, cement, ceramics and metallurgy.

Question: 7

What are the uses of Nuclear Chemistry?

Answer: 7

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It has vast application in medical treatment, preservation of food and generation of electrical power through nuclear reactors.

Question: 8

On the basis of properties, elements are divided into which groups?

Answer: 8

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On the basis of properties elements are divided into metals, non-metal, and metalloids

Question: 9

Name one solid, one liquid and one gaseous element present at room temperature?

Answer: 9

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Solid : Sodium, Iron Liquid: Bromine and Mercury Gas: Oxygen , Nitrogen, and Chlorine

Question: 10

Define Relative atomic mass?

Answer: 10

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"Relative atomic mass of an element is the average masses of atoms of that element as compound to 1/12th the mass of one atom of Carbon-12 isotope. Example: Mass of Na = 23 amu When atomic mass unit is expressed in grams, it is. 1 amu = 1.60x10-24 g

Question: 11

Define Industrial Chemistry and Analytical Chemistry.

Answer: 11

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Industrial Chemistry: "This branch of chemistry is related to the the industrial processes" It is associated with studies of properties uses and application of techniques for the preparation of industrial sales on large scale.

Question: 12

Define atomic mass unit. Why is it needed?

Answer: 12

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Atomic Mass Unit: The unit for relative atomic masses is called atomic mass unit. Symbol:Its symbol is amu. One atomic mass unit is 1/12th the mass of one atom of carbon -12th the mass of one atom of carbon-12th . When this atomic mass unit is expressed in grams, it is : 1 amu=1.66 x 10-24 g

Question: 13

Give the scope of biochemistry .

Answer: 13

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It is the branch of chemistry in which we study the structure , composition and chemical reaction of substances found in living organisms . It covers all chemical processes taking place in living organisms . Such as synthesis and metabolism of bio molecules like carbohydrates , proteins and fat . Biochemistry emerged as separate discipline when scientists began to study how living things obtain energy from food or how the fundamental biological changes occur during a disease . Examples of applications of biochemistry are in the fields of medicine , food science and agriculture etc

Question: 14

What is the significance of the symbol of an elements?

Answer: 14

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Significance of the symbol of an element: Symbols are used for elements instead of writing of their complete names. So, it takes less time save time and element can be recognized by that symbol in all over the world. For example oxygen,sulphur, Nitrogen

Question: 15

Define Chemistry?

Answer: 15

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The Branches of Science which deals with the composition, structure, properties and reactions of matter is called chemistry.

Question: 16

Define empirical formula and give examples.

Answer: 16

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It is the simplest whole number , ratio of atoms present in a compound." Empirical formula of benzene Empirical formula of Hydrogen peroxide

Question: 17

What is teh relationship between mass and mole of a substance?

Answer: 17

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The relationship between mass and mole of substance is given as following mass of substance = No of moles x Molar mass of substance

Question: 18

Which has more atoms :10g of Al or 10 g of Fe ?

Answer: 18

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10 g of A 1 has more atoms than 10 g of Fe

For A 1

Question: 19

What is radical

Answer: 19

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An atom or a group of atoms that have some charge and keeps in contact during a chemical reaction is called a radical e.g. Hydronium H₂O and carbonate CO₃^-2

Question: 20

What is the relationship between atomic number and atomic mass?

Answer: 20

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The relationship between atomic number and atomic mass is as following. A = Z = n Where A = mass number Z = Atomic number n= no of neutrons

Question: 21

Why atomic mass of an atom is defined as relative atomic mass?

Answer: 21

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ATomic mass of an atom is defined as relative atomic mass, because atomic mass of an atom is the mass which compares or relates with 1/12th mass of carbon 12 isotope.

Question: 22

Give the composition of milk .

Answer: 22

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Milk is a mixture of calcium , water ,sugar , fat , proteins , minerals, salts , and vitamins

Question: 23

Define relative atomic mass .

Answer: 23

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Relative atomic mass of an element is the average masses of atoms of that element as compared to 1 / 12th the mass of one atom of carbon -12 isotope

Question: 24

Give the composition of milk.

Answer: 24

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Milk is a mixture of calcium , water, sugar, fat, proteins, minerals, salts and vitamins.

Question: 25

How many atoms are present in one gram atomic mass of a substance?

Answer: 25

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One gram atomic mass of a substance is equal to Avogadro's number in which 6.023 x 1023 atoms are present

Question: 26

Which branch of chemistry deals with the structure and properties of naturally occurring molecules.

Answer: 26

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"Organic chemistry deals with the structure and properties of naturally occuriring molecules."

Question: 27

What is radical ?

Answer: 27

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An atom or a group of atoms that have some charge and keeps in contact during a chemical reaction is called a radical e,g Hydronium H₃O⁺ and CO₃ ^-2

Question: 28

Find out the mass of 3 moles of oxygen atoms.

Answer: 28

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3 x 16 = 48 g of oxygen are present in 3 moles.

Question: 29

How can you differentiate between organic and inorganic chemistry .

Answer: 29

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Organic chemistry : It is the study of the properties and behavior of hydrocarbons (compounds of carbon and hydrogen ) and their derivatives

Question: 30

Differentiate between empirical and molecular formula.

Answer: 30

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Empirical formula: it is the simplest whole number ratio of atoms present in a compound

e.g. Empirical formula of benzene is CH.

Question: 31

Define chemistry ? Explain two branches of chemistry .

Answer: 31

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Chemistry : The Branch of science which deals with the composition , structure, properties and reaction of matter is called chemistry

Question: 32

Which one has more formula units : 1g of NaClor 1 g KCL ?

Answer: 32

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NaCl has more formula units than KCl

For NaCl

Formula unit = Mass / Formula mass

= 1/58.5

= 0.017

Question: 33

Is atomic mass unit a SI unit of an atomic mass?

Answer: 33

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Yes , Atomic mass unit is SI unit of atomic mass.

Question: 34

What is atomic number, how it is represented?

Answer: 34

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"The atomic number of an element is equal to the number of protons present in the nucleus of its atoms." Representation:It is represented by "Z"

Question: 35

What is meant by variable valency?

Answer: 35

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Some elements show more than one combining power that is called variable valency for example, in Ferrous sulphate the valency of Iron is 2 whereas in ferric sulphate the valency of iron is 3

Question: 36

What is valency?

Answer: 36

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The combining capacity of an element with other elements is called valency For example. Valency of carbon is 4

Question: 37

What is Radical?

Answer: 37

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An atom or a group of atoms that have some charge and keeps in contact during a chemical reaction is called a radical e.g. Hydronium and carbonate.

Question: 38

Which branch of chemistry deals with preparation of paints and papers?

Answer: 38

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"Industrial chemistry deals with preparation of paints and papers."

Question: 39

How does homogenous mixture differ from heterogenous mixture ?

Answer: 39

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Homogenous mixture : Mixtures that have uniform composition through are called homogenous mixture

Question: 40

What are application of inorganic chemistry.

Answer: 40

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It has application is every aspect of chemical industry such as glass, cement, ceramics and metallurgy.

Question: 41

Differentiate between molecular mass and formula mas , which of the following is molecular formula ?

. H2O

.NaCl

.Kl

.H₂SO₄

Answer: 41

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Molecular mass :

The sum of atomic masses of all the atoms present in one molecule of a molecular compound is its molecular mass

Question: 42

What is free radical? Give example.

Answer: 42

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"Free radicals are atoms or group of atoms possessing odd number of electrons". Example: It is represented by putting a dot over teh symbol of an element e.g. H+,Cl-,H3C, Free radical are generated by teh homolytic breakage of the bond between 3 two atoms when the absorb heat or light energy A free radical is extremely reactive species as it has the tendencyto complete its octel.

Question: 43

is the mass of 1 mole of Oxygen and 1 mole of Sulphur same.

Answer: 43

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No, the mass of 1 mole of oxygen and 1 mole of sulphur atom is not same.

Question: 44

In which branch of chemistry deals with preparation of paints and papers?

Answer: 44

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"Industrial chemistry deals with preparation of paints and papers".

Question: 45

Define Biochemistry.

Answer: 45

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"It is branch of chemistry in which we study the structure, composition and chemical reactions of substances found in living organisms .

Question: 46

How can you justify that air is a homogenous mixture . Identify substance present in it ?

Answer: 46

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Air is a mixture formed by the physical mixing of the substance like nitrogen , oxygen ,carbon dioxide , noble gases and moisture and it has same composition throughout , so it is homogenous mixture

Question: 47

In which branch of chemistry behaviour of gases and liquid is studied?

Answer: 47

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The behaviour of gases and liquids is studied in the branch of chemistry called physical chemistry.

Question: 48

Define empirical formula and give example .

Answer: 48

48-861

_{It is the simplest whole number , ratio of atoms present in a compound}

Question: 49

What is the relationshp between atomic number and atomic mass?

Answer: 49

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The relation between atomic number and atomic mass is as following A = Z + n

Question: 50

State three reasons why do you thing soft drink is a mixture and water is a compound .

Answer: 50

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Soft drink is a mixture because :

1: Its components are not bounded chemically

2: The components do not have fix ratio

Question: 51

Which branch of chemistry deals with energy of atoms and its uses in daily life.

Answer: 51

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Nuclear chemistry deals with energy of atoms and its uses in daily life.

Question: 52

How many atoms are in I amu and I g of hydrogen .

Answer: 52

52-861

1 amu and 1 gram of hydrogen has 6.022x10²³atoms.

Question: 53

Define industrial chemistry and analytical chemistry

Answer: 53

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Industrial chemistry : This branch of chemistry is related to the industrial process . It is associated with studies of properties uses and application of techniques for the preparation of industrial sales on large scale

Question: 54

What is the relationship between empirical formula and formula unit.

Answer: 54

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All the organic compounds are represented by formula unit. Formula unit is also and empirical formula of Ionic compounds.

Question: 55

If 16 gram of oxygen contains 1 mole of oxygen atoms calculate the mass of one atom of oxygen in grams.

Answer: 55

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16 g of oxygen = 1 mole of oxygen

Mass of one atom of oxygen = 16 grams.

Question: 56

Find out the mass of 3 moles of oxygen atoms .

Answer: 56

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3x16 = 48g of oxygen are present in 3 moles

Question: 57

How many atoms are present in 16 g of O and 8g of S?

Answer: 57

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16 grams of oxygen has 6.022 x 10²³atoms and 8 grams of sulphur has 1.055x10²³atoms.

Question: 58

What do you mean by 1 atom carbon and 1 gram atom of Carbon.

Answer: 58

58-861

One atom of carbon has its atomic mass which is 12 amu . But when this mass of carbon atom is expressed in gram then it is known as gram atomic mass. As 1 gram of carbon =12.0 g.

Question: 59

Which one has more molecules : 9 g of water or 9 g of sugar C₁₂ H₂₂O₁₁ ?

Answer: 59

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9g of water has more molecules than 9 g of sugar because moles of water are more than sugar

For water

Question: 60

State three reasons why do you think air is a mixture and water a compound

Answer: 60

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Air (mixture)

1: Mixture is formed by the simple mixing up of the substances

2: Air does not have a sharp and fixed melting point

3: Air has heterogenous mixture composition

Question: 61

How many times is 1 mole of oxygen atom heavier than 1 mole of hydrogen atom?

Answer: 61

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One mole of oxygen atom is 16 times heavier than the one mole of hydrogen.

Question: 62

Which six elements constitute 99% of body mass and what are their percentages ?

Answer: 62

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Following six elements constitute 99%of body mass

Oxygen 65%

Hydrogen 10%

Calcium 1.5 %

Carbon 18%

Nitrogen 3%

Phosphorous 1.5%

Question: 63

Differentiate between homoatomic and heteroatomic molecules with examples .

Answer: 63

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Homoatomic molecules : A molecule containing same type of atoms is called homoatomic molecule

Question: 64

Write down the chemical reactions of chlorine with hot and cold aqueous solutions of sodium hydroxides

Answer: 64

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Chlorine reacts with cold dilute NaOH to give sodium hypochlorite .

2NaOH +Cl₂➜ NaCl+ NaOCL +H₂O

Question: 65

Write chemical reaction of H₂with F2 and Cl₂ .

Answer: 65

65-861

Reaction of H₂ with F₂: Flourine combines with hydrogen even in the dark and cold state

H2 +F2➜ 2HF

Question: 66

Differentiate between molecule or molecular ion ?

Answer: 66

66-861

Molecule :

1: It is the smallest particle of a compound which can exist independently and shows all the properties of that compound

2: It is always neutral

3: It is formed by the combination of atoms

4: It is a stable unit

Question: 67

Write down chemical reaction of sodium with H₂ and Cl_{2 .}

Answer: 67

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Reaction of hydrogen with sodium :

Sodium reacts with hydrogen at high temperature to form hydrides

2 Na + H₂➜ 2NaH

Question: 68

What are applications of inorganic chemistry?

Answer: 68

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It has application in every aspect of chemical industry such as glass , cement , ceramics and metallurgy

Question: 69

Explain why are oxygen and hydrogen considered elements whereas water as a compound ?

Answer: 69

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Hydrogen and oxygen are element because

1: Each one of it consists of same type of atoms

Question: 70

Which branch of chemistry deals with preparation of paints and papers ?

Answer: 70

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Industrial chemistry deals with preparation of paints and papers .

Question: 71

Define Biochemistry ? Describe scope of biochemistry and give two examples of biochemistry.

Answer: 71

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The branch of science concerned with the chemical and physico-chemical processes and substances that occur within living organisms.

Question: 72

Write name of any two elements found in gaseous state

Answer: 72

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Nitrogen and oxygen both found in gaseous state

Question: 73

State the nature and name of the substance formed by combining the following

1: Zinc + Copper

2: Water +Sugar

3: Aluminum +Sulphur

4: Iron + Chromium + Nickle

Answer: 73

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1:Zinc + Copper

It will be a mixture called a brass (alloy)

Question: 74

Which of the following cases the number of hydrogen atoms is more?

Answer: 74

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1 mole of NH3 has more hydrogen atoms than 2 moles of HCL

Question: 75

Name one solid , one liquid and one gaseous element present at room temperature ?

Answer: 75

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Sodium ( Na) , Iron ( Fe)

Question: 76

Differentiate between homogenous and heterogenous mixture .

Answer: 76

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Homogenous Mixture : Mixtures that have have uniform composition throughout are calledhomogenous mixture

Question: 77

State the nature and name of the substance formed by combining the following

1: Zinc + Copper

2: Water +Sugar

3: Aluminum +Sulphur

4: Iron + Chromium + Nickle

Answer: 77

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2: Water + Sugar

It will be a solution or mixture called sugar syrup

Question: 78

Define atomic mass unit . Why is it needed ?

Answer: 78

78-861

The unit for relative , atomic mass unit

Question: 79

Is atomic mass unit a SI unit of an atomic mass ?

Answer: 79

79-861

Yes ,atomic mass unit is SI unit of atomic mass

Question: 80

What is meant by variable valency ?

Answer: 80

80-861

Some elements show more than one combining power (valency) that is called variable valency

Question: 81

Classify the following into elements , compound and mixture ?

1: He and H2

2: CO and Co

3: Water and milk

4: Gold and brass

5: Iron and steel

Answer: 81

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Elements :

He , H₂ ,Co, Gold , Iron

Question: 82

Define chemistry ?

Answer: 82

82-861

The branch of science which deals with the composition , structure , properties and reactions of matter is called chemistry .

Question: 83

How many atoms of sodium are present in 3 moles of sodium and what is the mass of it ?

Answer: 83

83-861

Number of atoms of sodium are present in 3 moles = 3x6.02x10²³ atoms

= 1.806x 10²⁴

Question: 84

In the basis of properties , elements are divided into which group ?

Answer: 84

84-861

On the basis of properties elements are divided into metals , non-metals and metalloids

Question: 85

An element has an atomic number 17 , how many electrons are present in K and M shells of an atom ?

Answer: 85

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K=2 , L= 8 , M=7

An atom has atomic number 17, in first shell (K) contains 2 electrons , then second shell called (L) shell have 8 electron and 3rd shell (M) have 7 electrons

Question: 86

What elements do the following compound contains ?

Answer: 86

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Sugar ,common salt , lime water and chalk

Question: 87

Differentiate between ions and free radicals ?

Answer: 87

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Ions :

1: These are atoms which bear some charge

2: They exists in solution or in crystal lattice

3: Their formation is not affected by the presence of light

Question: 88

What is the significance of chemical formula ?

Answer: 88

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1: It represents the name of the substance e.g H₂O (water)

Question: 89

Define industrial chemistry and analytical chemistry ?

Answer: 89

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Industrial chemistry : It is the branch of chemistry that deals with the manufacturing of chemical compounds on commercial scale

Question: 90

Give the composition of earth crust with respect to three major elements .

Answer: 90

90-861

Earth crust is formed by three major elements having following percentages

Question: 91

Why atomic mass of an atom is defined as relative atomic mass ?

Answer: 91

91-861

Atomic mass of an atom is defined as a relative atomic mass , because atomic mass of an atom is the mass which compares or relates with 1/12th mass of carbon 12 isotope

Question: 92

Differntiate between biochemistry and industrial chemistry .

Answer: 92

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Biochemistry : Biochemistry is the branch of chemistry in which w study the structure , composition , and chemical reaction of substances found in living organisms

Question: 93

Define organic chemistry and which industries covered by it

Answer: 93

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Organic chemistry : it is the study of covalent compounds of carbon and hydrogen and its derivatives

Question: 94

Differentiate between substance and mixture .

Answer: 94

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Substance : A piece of matter in pure form is termed as substance

e,g Glucose (C₆H₁₂O₆ ) Oxygen

Question: 95

What is the relationship between mass and mole of a substance ?

Answer: 95

95-861

the relationship between mass and mole of a substance is given as following

Question: 96

What are the uses of nuclear chemistry ?

Answer: 96

96-861

It has vast application in medical treatment , preservation of food , and generation of electrical power nuclear reactors

Question: 97

What is the atomic number , how it is represented ?

Answer: 97

97-861

The atomic number of an element is equal to the number of protons present in the nucleus of its atoms

Question: 98

Which branch of chemistry deals with energy of atoms and its uses in daily life ?

Answer: 98

98-861

Nuclear chemistry deals with energy of atoms and its uses in daily life

Question: 99

Name the elements represented by the following symbols W, Ba , Hg and Na

Answer: 99

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Tungsten W , Barium B , Mercury Hg , Sodium Na

Question: 100

What is valency ?

Answer: 100

100-861

The combining capacity of an element with other element is called valency

Question: 101

What was the thickness of gild foil used in Rutherford's atomic model ?

Answer: 101

101-861

0.00004 cm thick gold foil was used by Rutherford in his experiment

Question: 102

How many amu 1 g of a substance has ?

Answer: 102

102-861

1.66x 10^-24g +1 amu

1g = 1/1.66x 10^-24amu

Question: 103

Explain difference between physical chemistry and biochemistry .

Answer: 103

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Physical chemistry: physical chemistry IS defined as the branch of chemistry that deals with the relationship between the composition and physical properties of matter , along with changes in them

Question: 104

How many molecules of water are present in half mole of water ?

Answer: 104

104-861

Water molecules in half moles = 1/2x6.02x10²³

= 3.01x10²³molecules

Question: 105

What is matter ?

Answer: 105

105-861

Anything which has mass and occupy space is called matter

Question: 106

How many atoms are in 1 amu and 1g of hydrogen (H)?

Answer: 106

106-861

1amu and 1 gram of hydrogen (H) has 6.022x10²³ atoms and 8 grams of sulphur has 1.005x10²³atoms

Question: 107

What do you mean by 1 atom of C and 1 gram of atom of C ?

Answer: 107

107-861

One atom of carbon has its atomic mass which is 12 amu . But when this mass of carbon atom atom is expressed in grams then it is known as gram atomic mass . As 1 gram of carbon = 12.0 g

Question: 108

Differentiate between empirical and molecular formula .

Answer: 108

108-861

Empirical formula: It is the simplest whole number ratio of atoms present in a compound

Question: 109

Define biochemistry ?

Answer: 109

109-861

It is the branch of chemistry in which we study the structure , composition , and chemical reaction of substances found in living organisms (i-e humans ,animals and plants )

Question: 110

What is meant by element ? Explain with example .

Answer: 110

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Element is a substance which is made up of some types of atom , having same atomic number and it cannot be dissolved into simple substances by ordinary chemical means

Question: 111

Differentiate between atom and ion ?

Answer: 111

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Atom :

1: It is the smallest particle of an element

2: It can or cannot exists independently and can take part in a chemical reaction

3: It is electrically neutral

Question: 112

What is the relationship between atomic number and atomic mass ?

Answer: 112

112-861

The relationship between atomic number and atomic mass is as following

A = Z+n

Where A = mass number

Z = atomic number

N = no of electrons

Question: 113

How many atoms are present in one gram atomic mass of a substance ?

Answer: 113

113-861

One gram atomic mass of a substance is equal to Avogadro's number in which 6.023x10²³atoms are present

Question: 114

Magnesium has electronic configuration 2,8,2

a: How many electrons are in outermost shell ?

b: In which sub-shell of outermost shell electrons are present ?

c: Why magnesium tends to lose electron ?

Answer: 114

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a: There are two electrons in outermost shell

b : In sub-shell of outermost shell electron are present

1s² , 2s² , 2p⁶ .3s²

Question: 115

How many sub-shells are there in second shells ?

Answer: 115

115-861

Two sub-shells s and p are present in second shell L

Question: 116

Differentiate between nuclear chemistry and environmental chemistry .

Answer: 116

116-861

Environmental chemistry:

1 :The branch of chemistry in which we study about components of the environment and effect of human activity on the environment

2 :it is also concerned with other sciences like biology, geology

3: Save environment from pollution

Question: 117

How many atoms are present in 16g of Oand of S ?

Answer: 117

117-861

16 grams of oxygen has 6.022x10²³atoms and 8 grams of sulphur has 1.055x10²³ atoms

Question: 118

In which branch of chemistry are the metabolic processes of carbohydrates and proteins studied ?

Answer: 118

118-861

In biochemistry metabolic processes carbohydrates and proteins are studied

Question: 119

Write any two elements found in the liquid state at room temperature .

Answer: 119

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Mercury and bromine are two elements found in the liquid state at room temperature

Question: 120

Which term is used to represent the mass of 1 mole of molecules of a substance ?

Answer: 120

120-861

Gram molecular mass

Question: 121

Which branch of chemistry deals with the structure and properties of naturally occurring molecules ?

Answer: 121

121-861

Organic chemistry deals with the structure and properties of naturally occurring molecules

Question: 122

What is free radical ? Give example.

Answer: 122

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Free radical : Free radical are atoms or groups of atoms possessing odd number (unpaired ) electrons.

Question: 123

Find out molecular mass and formula masses of the following

Na₂SO₄ ,ZnSO₄ , and CuCO_3.

Answer: 123

123-861

Formula mass of Na₂SO₄ = 2(23)+32+4 (16)

= 46+32+64
=142 amu

Question: 124

Identify the following as empirical or molecular formula :

H₂O₂ ,CH₄, C₆H₁₂O₆ , C₁₂H₂₂O₁₁ ,BaCO₃ ,KBr

Answer: 124

124-861

Empirical formula : KBr , BaCO_{3 ,}CH₄

Question: 125

Differentiate shell and sub-shell with example of each ?

Answer: 125

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Shell (Orbit):

The circular orbits of specific energy are called shells or energy levels

Question: 126

In which branch of chemistry behaviour of gases and liquid is studied ?

Answer: 126

126-861

The bahaviour of gases and liquid is studied in the branch of chemistry called physical chemistry

Question: 127

Why does an electron fill 2p orbital and then 3s and then 3s orbital ?

Answer: 127

127-861

As we know that electrons that electrons fill the shells as order of their increasing energy , i-e lower energy level is occupied first then the high energy level and so on . 2p orbital has lower energy than 3s orbital that is why 2p orbital is first filled and then 3s orbital

Question: 128

How was it shown that atomic nuclei are positively charged ?

Answer: 128

128-861

The deflection of a few particles proved that there is a center of positive charge in an atom , , which is called nucleus of an atom

Question: 129

What is the relationship between empirical formula and formula unit ?

Answer: 129

129-861

All the ionic compounds are represented by formula unit . Formula unit is also and empirical formula of ionic compounds

Question: 130

What is the significance of the symbol of an element ?

Answer: 130

130-861

Symbol means identification , in chemistry it is used for the representation of chemical name of an element . In chemical equation whole name of an element is difficult to write , because the formula or chemical equation becomes too lengthy . Thus symbol makes an easy representation and understanding in this case

Question: 131

Write any two applications of inorganic chemistry.

Answer: 131

131-861

Inorganic chemistry has applications in following aspects of the chemistry industry

Question: 132

Why does 10 g nitrogen gas contain the same number of molecules as 10g of carbon monoxide ?

Answer: 132

132-861

Number of moles of nitrogen gas = 10/28 =0.35mol

Number of molecules of N₂ = 0.35x0.22x10²³

=2.107x10²³

Question: 133

Write down the name of any two elements which were discovered in early ages .

Answer: 133

133-861

Following elements were discovered in early ages

Question: 134

Why cesium requires little energy to release its one electron present in the their outermost shell ?

Answer: 134

134-861

Cesium is the 2nd last element of 1st group . It has large size and less force and less force of attraction between the nucleus and valence electron , as a result small amount of energy is required to remove electron from the valence shell

Question: 135

Write down the electronic configuration of Al³⁺. How many electrons are present in its outer most shells

Answer: 135

135-861

Al³+ = 1s² ,2s²,2p⁶

Question: 136

Define matter and mixture .

Answer: 136

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Matter : anything that has mass and occupies space is called matter . Matter exists in three physical states , solid , liquid , gas

Question: 137

Write difference between physical and chemical properties .

Answer: 137

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Chemical properties :

1: It depends upon the composition of the substance

2: When a substance undergoes a chemical change , its composition change and a new substance is formed .

Example : When hydrogen react with oxygen , it form water , chemical change

Question: 138

What isAvogadro's number?

Answer: 138

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Avogadro,s Number:

The number of particles present in one mole of a substance is called Avogadro's number. Its value is 6.02 x 10²³. it is represented by Na

Question: 139

Is the mass of 1 mole of O and 1 mole of S same ?

Answer: 139

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Nothe mass of 1 mole of O and 1 mole of S is not same

Question: 140

Give few properties of canal rays .

Answer: 140

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a: Deflection of these rays in electric and magnetic field proved that these were positively charged

Question: 141

Do you know any element having no neutron in its atom ?

Answer: 141

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Isotope of hydrogen , protium have one proton and no neutrons in it

Question: 142

What is atomic number of phosphorous ? Write down its electronic configuration .

Answer: 142

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Atomic number of phosphorous (P) is 15

Electronic configuration

1s² , 2s² ,2p⁶ ,3s² ,3p³

Question: 143

Why melting point and boiling points of ionic compounds are high?

Answer: 143

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Melting and boiling of ionic compounds are high because thy consists of positive and negative ions . There exists very strong electrostatic interaction between these charged ions . That is why a lot of force is required to break these forces

Question: 144

For what purpose U-235 is used ?

Answer: 144

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When U-235 is bombarded with slow moving neutrons , uranium nucleus breaks up to produce Barium-139 and Krypton -94 and three neutrons

Question: 145

What is difference between compound and mixture / Give example .

Answer: 145

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Compound :

1:It is formed by chemical combination of atoms of element

2:Its components lose their own properties and produce new substance that have entirely different properties

Question: 146

If 16g of oxygen contains 1 mole of oxygen atoms calculate the mass of one atom of oxygen in grams

Answer: 146

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16g of oxygen =1 mol of oxygen

Mass of one atom of oxygen = 16 grams

Question: 147

What will be the nature of charge on an atom when it loses an electron or when it gains an electron ?

Answer: 147

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When it lose an electron it become positive an when it gains and electron it become negative

Question: 148

The atomic symbol of a phosphorous ion is given as ³¹_15P3-

a : How many protons , electrons , and neutrons are there in ion³¹_15P3- ?

b: What is the name of ion ?

c:Draw electronic configuration of ion .

d: Name noble gas which has some electronic configuration as phosphorous ?

Answer: 148

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Proton = 15

Electron = 18

Neutron = 16

b: Phosphorous ion

c: E.C =1s² , 2s² , 2p⁶ , 3s² ,3p⁶

Question: 149

Write two properties of gases

Answer: 149

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1: Molecules of gases are always in state of continuous motion . They have very high K.E .

Question: 150

Give few properties of cathode rays .

Answer: 150

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a: These rays travel in a straight line perpendicular to the cathode surface

Question: 151

What observations were the observations made by Rutherford ?

Answer: 151

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There were two observations .

Question: 152

How many electrons are present in sub-shell ?

Answer: 152

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s can have 2 electrons

p can have 6 electrons

d can have 10 electrons

f can have 14 electrons

Question: 153

What is the empirical formula of acetic acid (CH₃COOH)? Also calculate the molecular mass of acetic acid .

Answer: 153

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Empirical formula of acetic acid is CH₂O

Question: 154

What is quantum ?

Answer: 154

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Quantum means fixed energy . It is the smallest amount of energy that can be emitted or absorbed as electromagnetic radiation

Question: 155

Name the particle which determine the mass of an atom ?

Answer: 155

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Protons and neutrons determine the mass of an atom

Question: 156

Briefly describe the mobility of gases.

Answer: 156

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Gas molecules are always in state of continuous motion . They can move from one place to another because gas molecules have high kinetic energy . This continuous motion of gases is called mobility of gases

Question: 157

How many times is 1 mole of oxygen atoms calculate the mass of one atom of oxygen in grams

Answer: 157

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One mole of oxygen atom is 16 times heavier than the one mole of hydrogen

Question: 158

Why do the isotopes of an element have different atomic number masses?

Answer: 158

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As isotopes of an element have same atomic mass . Mass number depends upon number of protons and neutrons . Isotopes of an element have the same number of proton but only differ in their neutrons number

Question: 159

How many atoms of hydrogen present in 1 mole of water ?

Answer: 159

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1 mole of water = 6.02 x 10²³molecules

1 mole of water has H atom =1x 6.02x10²³atoms

= 6.02 x 10²³

Question: 160

Write two properties of liquid state of matter

Answer: 160

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1: Liquid have fixed volume but no fixed shape . It attains the shape of container in which it is kept

Question: 161

What was the pressure inside the discharge tube in discovery of electron?

Answer: 161

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The pressure inside the tube was kept 10^-4 atm

Question: 162

How is periodicity of properties dependent upon the numbers of protons in an atom ?

Answer: 162

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In periodic table from left to right number of protons increase regularly by 1 from atom to atom . Therefore nuclear charge will increase . Due to change in nuclear charge the properties of an atom were found repeating after regular intervals . Hence periodicity of properties dependent upin the number of protons in an atom

Question: 163

How many electrons will be in M-shell of an atom having atomic number 15 ?

Answer: 163

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K L M

2 8 5

5 electrons are present in M shell of an atom having atomic number 15

Question: 164

How can you prove that angular momentum is quantized ?

Answer: 164

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mvr =nh/2π

The angular momentum of first orbit is (n=1)

mvr = 6.63x10^-34/2x 3.14

Question: 165

Define modern periodic law ?

Answer: 165

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In 1913 H.Moseley given Modern law

Properties of elements are periodic function of their atomic masses

Question: 166

Define atom according to Dalton ?

Answer: 166

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Atom is an indivisible , hard ,dense and sphere

Question: 167

What do you mean by group or median in periodic table ?

Answer: 167

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The horizontal rows in periodic table called periods and vertical columns in the periodic table are called groups

Question: 168

Define relative atomicmass based on C-12 scale.

Answer: 168

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Relative Atomic Mass:

The relative atomic mass of an element is the average mass of atoms of the element as compare to 1/11th the mass of one atom of carbon 12 isotope

Question: 169

How was it is proved that whole mass of an atom is located at its center ?

Answer: 169

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The complete rebounce of a few particles show that the nucleus is very hard , dense and contain all mass of an atom

Question: 170

Define chemical formula and give one examples .

Answer: 170

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Definition : A chemical formula is the symbolic representation the elements in the compounds and the ratio of the elements to one another

Question: 171

A patient has goiter . How will it be detected ?

Answer: 171

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The radioactivity isotopes are used as tracers in medicine to diagnose the presence of tumor in human body . Isotope of I-131 is used for diagnose of goiter in thyroid gland

Question: 172

Define isotope ?

Answer: 172

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Isotopes are defined as the atoms of elements that have same atomic number but different mass number

Question: 173

Why the bond between an electropositive and electronegative atom is ionic in nature ?

Answer: 173

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Electropositive elements lose electrons while electronegative elements gain electrons . That's why both combine and forms ionic bond

Question: 174

What is meant by relative molecular mass?

Answer: 174

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Relative molecular mass:

The ratio of the average mass of one molecule of an element or compound to one twelfth of the mass of an atom of carbon- 12

Question: 175

How is the goiter in thyroid gland detected ?

Answer: 175

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Iodine -131 is used fir the diagnosis of goiter in thyroid gland

Question: 176

What is the nature of charge on cathode rays ?

Answer: 176

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Their deflection in electric and magnetic field proves that they have negative charge

Question: 177

Differentiate between boiling and melting point .

Answer: 177

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Melting point : The temperature at which the solid starts melting and exist in dynamic equilibrium with liquid state is called melting point

Question: 178

A long as electron remains in an orbit , it does not emit or absorb energy , when does it emit or absorb energy ?

Answer: 178

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When an electron jumps from lower orbit to higher orbit . It absorbs energy and when it jumps from higher orbit to lower orbit . It radiates energy . This change in energy ,

△E given by following Plank's equation

Question: 179

Define electronic configuration ?

Answer: 179

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Electronic configuration : The distribution of electrons around the nucleus in various shells and sub-shells according to increasing energy , is called electronic configuration

Question: 180

Define homogenous mixture and give example .

Answer: 180

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Homogenous mixture: The mixture having uniform composition is calledhomogenous mixture

Question: 181

Ionic bond is stronger than covalent bond . Explain .

Answer: 181

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Ionic bond formed between two opposite charges and electrostatic forces . That's why ionic compound is stronger than covalent bond

Question: 182

If an element has atomic number 13 and atomic mass 27 , how many electrons are there in each atom of the element?

Answer: 182

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Atomic number of an element (Z) =13

Mass no.of an atom (A) =27

A the total number of electrons in an atom is equal to its atomic number (Z) ,so it will have 3s electrons

Question: 183

Why the rate of diffusion gases is rapid than that of liquids ?

Answer: 183

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The rate of diffusion of gases is rapid than that of liquid due to the less attractive forces among the gas molecules than liquids . Gas molecule moves randomly and spread around

Question: 184

What is the capacity of the K,L,M,N shells ?

Answer: 184

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K shell can accommodate 2 electron

L shell can accommodate 8 electrons

M shell can accommodate 18 electrons

N shell accommodate 32 electrons

Question: 185

In which pattern modern periodic table was arranged?

Answer: 185

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According to increasing atomic number.

Question: 186

Write four examples of mixture .

Answer: 186

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1: Air is a mixture of nitrogen , carbon dioxide , noble gasses and water vapours

Question: 187

When do electrons emit or absorb energy ?

Answer: 187

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A long as electron remain in a particular orbit it does not radiate or absorb energy, The energy is emitted or absorbed only when an electron jumps from one orbit to another

Question: 188

Calculate molecular mass of NH3.

Answer: 188

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Molecular mass :

NH3 =14+1*3

=17a.m.u

Question: 189

Why densities of gases are less than liquids ?

Answer: 189

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Gases have low density than liquids and solids . It is due to light mass and more volume occupied by the gas molecules . Gas density is expressed in grams per dm³. Whereas liquid and solid densities are expressed in grams per cm³ i-e liquids and solids are 1000 time denser than gases

Question: 190

Explain plum pudding theory .

Answer: 190

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Thomson put forth his plum pudding theory . He postulated that atoms were solid structures of positively charge with tiny negative particles stuck inside . It is like plum in the pudding

Question: 191

Why shielding effect of electron makes action formation easy ?

Answer: 191

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As we move down in a group more and more shells come come between valence shell and the nucleus of atom , additional shell reduce the electrostatic force of attraction felt by the electron present in the outermost shell , and the shielding effect increases resultantly , and the electrons can be taken away , easily and cations form

Question: 192

From which word atom derived ?

Answer: 192

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Atom is derived from latin word 'Atomos' meaning indivisible

Question: 193

What is matter ? How many states it has ?

Answer: 193

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Matter is any thing that has mass and occupies space .

Question: 194

Define element?

Answer: 194

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Eelement:

Eelement is define as the substance which is made up of atoms of the same type or a substance in which all the atoms have the same atomicnumber, e.g.

Sodium (Na) and Hydrogen (H) etc

Question: 195

What type of covalent bond is formed in nitrogen molecule?

Answer: 195

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In nitrogen molecule. three bond pairs are involved in bond formation. This type is called triple covalent bond. Three small lines are used to indicate these three pairs of electrons between those atoms in the molecules of such compounds.

Question: 196

Define evaporation and give example ?

Answer: 196

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Evaporation: The conversion of liquid into vapours called evaporation .

Question: 197

Electronic configuration of Cl^-ion

Answer: 197

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Cl^-1s² ,2s²,2p⁶ ,3s² ,3p⁶

Question: 198

Why and how are element arranged in 4th period ?

Answer: 198

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Elements are arranged in 4th period according to increasing atomic number . The 4th period contains 18 elements beginning with potassium and ending with krypton . As a rule . 4th period elements fill their 4th subshells in that order however there are exception such as chromium

Question: 199

Give electronic configuration of hydrogen ?

Answer: 199

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Electronic configuration of ¹1H is 1s¹

Question: 200

How free radical is formed ?

Answer: 200

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Free radicals are formed by the homolytic (equal) breakage of bond between two atoms when they absorb heat or light energy

Question: 201

What is classical theory of radiation . How it is differ from quantum theory ?

Answer: 201

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According to classical theory of radiation electrons being the charge particle should release energy continuously and they should ultimately fall into a nucleus . It differ from quantum theory because quantum means fixed energy it is the smallest amount of energy that can be emitted or absorb as electromagnetic radiation

Question: 202

Ionic compounds are solids. Explain

Answer: 202

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Ionic compounds are made up of positively and negatively charged ions . Thus they consists of ions and not molecules . These positively charges ions are held together in a solid or crystal form

Question: 203

What are blocks ? How many blocks are present in periodic table ?

Answer: 203

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On the basis of completion of a particular sub shell , element with similar sub-shell electronic configuration are referred as a block of elements . Four blocks are present in periodic table . s,p,d,f

Question: 204

What are shells ?

Answer: 204

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Shells are specific energy levels around nucleus in which electron resolve

e.g K,L,M,N

Question: 205

Write two properties of covalent compounds

Answer: 205

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1: They have usually low melting and boiling points

Question: 206

Give the trend of ionization energy in a period ?

Answer: 206

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If we move from left to right in a period the value of ionization energy increases . Because the size of atom reduce and valence electrons are held strongly by the electrostatic force of nucleus . Therefore elements on left side of the periodic table have low ionization energies as compared to those on right side of the periodic table

Question: 207

How many neutrons are present in C-12 and C-13 ?

Answer: 207

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C-12 C-13

P=6 P=6

N=12-6=6 N=13-6=7

Question: 208

Differentiate bonding electrons and non-bonding electrons•

Answer: 208

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The valence electrons which are involved in chemical boding, are termed as bonding electrons. e.g.

The valence electron of sodium is bonding electrons

₁₁Na K L M

2 8 1

Question: 209

What is relationship between Empirical formula and Molecular formula ?

Answer: 209

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The relationship between Empirical formula and Molecular formulais given as

Molecular formula = (Empirical formula)*n

When n = 1,2 ,3 and so on

Question: 210

Explain how anode rays are formed from the gas taken in the discharge tube .

Answer: 210

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Anode rays are produced when the cathode rays collide with residual gas molecules present in the discharge tube and ionize them as follows

M+ le^-➜ M⁺ +2e^-

Question: 211

What is the capacity of shells ?

Answer: 211

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The number of electrons accommodated by the shell called capacity of shell

Question: 212

What is compressibility?

Answer: 212

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Decrease of volume by increasing pressure is called compressibility of that thing like gases . Gases are highly compressible due to empty spaces between their molecules

Question: 213

How does homogeneousmixture differ from heterogeneous mixture?

Answer: 213

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The mixture that has uniform composition throughout is called homogeneous mixture which composition is not uniform throughout e.g. soil, rock and wood etc.

Question: 214

Define symbol and valency with example .

Answer: 214

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Symbol : The representation of any element with one or two english letters is called symbol.

Question: 215

Soft drink is a mixture while water is compound . Give the reason .

Answer: 215

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Water : Water forms by the chemical reaction of hydrogen and oxygen . that's why it is called compound

Question: 216

Give one example each of the use of radioactive isotope in medicine and radiotherapy ?

Answer: 216

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Radioactive isotopes is used in medicine

Iodine 131

Radioactive isotopes used in radiotherapy

P-32

Sr-90

Co-60

Question: 217

Show the state of Dynamic equilibrium in liquid and vapours with the help of diagram .

Answer: 217

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From the open surface of a liquid , molecules evaporates and mix up with the air but when we close a system ,evaporated molecules start gathering over the liquid surface . Initially the vapours condense slowly to return to liquid . After sometimes condensation process increases and a stage reaches when the rate of evaporation becomes equal to rate of condensation . At that stage the number of molecules coming back (condensing) to liquid . This state is called Dynamic equilibrium

Question: 218

Why shielding effect of electrons makes action formation easy ?

Answer: 218

218-861

As we move down in a group more and more shells come between valence shell and the nucleus of an atom , additional shell reduce the electrostatic force of attraction felt by the electron present in the outermost shell and the shielding effect increases resultantly , and electrons can be taken away , easily and cations form

Question: 219

What are meant by coordinate covalent compounds ?

Answer: 219

219-861

1: Properties of coordinate covalent compounds are similar to those of covalent compounds . They are unsoluble in water , don't ionize so make solution on dissolving in organic solvent

Question: 220

Which carbon isotope use in carbon dating ?

Answer: 220

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C-14 used in carbon dating

Question: 221

What is diffusion ? Explain with example .

Answer: 221

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Diffusion : The process in which molecules more from the area of higher concentration move to the area of lower concentration until the state of equilibrium is achieved is called diffusion

Question: 222

Write the relation between empirical formula and molecular formula

Answer: 222

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There is a relationship betweenempirical formula and molecularformula which is given as:

Molecular formula= (empirical formula

Where n= 1, 2, 3,,,,,,

Question: 223

Define nuclear fission reaction .

Answer: 223

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A reaction in which heavy nuclear splits up into two nuclei by absorbing show moving next ions

Question: 224

What is the difference between Mendeleev's and modern periodic law ?

Answer: 224

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Mendeleev's periodic law :

Properties of the element are periodic function of their atomic masses is called Mendeleev's periodic law

Question: 225

How many elements are in 3rd period, write their names and symbols?

Answer: 225

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There are eight elements in 3' period, sodium(Na), magnesium(Mg) .aluminium (AI).silicon(Si),phosphorus(P),sulphur(S),chlorine(Cl),argon(Ar)

Question: 226

How is periodicity of properties dependent upon the number of protons in an atom ?

Answer: 226

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In periodic table from left to right number of protons increases . Due to change in nuclear charge the properties of an atom were found repeating after regular intervals . Hence periodicity of properties dependent upon the number of proton in an atom

Question: 227

What is the valency id following ?

(A) Barium (B) Nitrogen (C) Sodium (D) Sulphur

Answer: 227

227-861

Elements valency

1: Barium 2

2: Nitrogen 3

3: Sodium 1

4: Sulphur 2

Question: 228

How meat can be preserved ?

Answer: 228

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Table salt is the most important ingredient for curing meat and is used in large quantities . Salt kills and inhibits the growth of putrefying bacteria by drawing water out of the meat . Concentrations of salt up to 20% are required to kill most of the species of unwanted bacteria . Once properly salted , the meat contains enough salt to prevent the growth of many undesirable microbes

Question: 229

Convert -30°C to K unit

Answer: 229

229-861

As we know that

(T)k = (T)°C +273

By putting°C=-30°

(T)k = (-30)°C +273

(T)k = (-30+273)°C

(T)k = 243°C

Question: 230

Who discovered proton , electron , neutron ?

Answer: 230

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In 1886, Goldstein discovered positively charged particles called protons . In 1897 , J.J Thomson found in an atom , the negatively charged particles known as electron . In 1932 James Chadwick discovered neutron

Question: 231

An element has 5 electron in M shell . Find out its atomic number ?

Answer: 231

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The number of this element will be 15

Question: 232

Calculate the formula mass of the sodium sulphate .

Answer: 232

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Formula mass of the sodium sulphate :

Na2so4 =2(23) +(32)+4(16)

=46+32+64

=142amu

Question: 233

Why the size of atom does not decrease regularly in periods ?

Answer: 233

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The atomic size does not decrease regularly in periods due to presence of transition elements . The size of atom first decreases then increases

Question: 234

Define effusion . Give example .

Answer: 234

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Effusion : Effusion is defined as the escaping of gas molecules through tiny holes into a space with lesser pressure

Question: 235

Difference between molecular mass and formula mass.

Answer: 235

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Molecular Mass:

The sum of the atomic mass of all the elements present in a molecule is called as Molecular Mass.

Question: 236

Whether the density of gases increase on cooling ?

Answer: 236

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The density of gases increasing by cooling because their volume decreases and molecules of gases came close to each other

Question: 237

Calculate no of carbon atoms in one mole C₆ H₁₂ O₆

Answer: 237

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6 atoms of carbon are present in one mole of glucose

Question: 238

Define ionic bond and ionic compounds .

Answer: 238

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Ionic bond : The type of chemical bond which is formed due to complete transfer of electron from one another is called ionic bond

Question: 239

What is mean by cation and anion? Explain with example.

Answer: 239

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Cation:

The cations are formed when an atom loses electrons from its outmost shells. For example cations are Na⁺ , K⁺, Ca⁺²

Na ______> Na⁺ + 1e^-

Question: 240

What are the defects of Mendeleev's periodic table or why improvement was make in Mendeleev's periodic table?

Answer: 240

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There are two defects in Mendeleev's periodic table:

Question: 241

Calculate the gram molecule in 40g of phosphoric acid

Answer: 241

241-861

Molar mass of phosphoric acid H₃PO_{4 = 3+31+64=98}

Question: 242

Why ionic compounds are easy soluble in water?

Answer: 242

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Water is polar compound while ionic compound dissolves and forms cation and anion . Cation makes force of attraction with negative pole of water , while anion with positive pole of water and dissolve in water

Question: 243

Why cesium (At.No.55 ) requires little energy to release its one electron present in their outermost shell ?

Answer: 243

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Cesium is the 2nd last element of 1st group . It has large size and less force of attraction between the nucleus and valence electron , as a result small amount of energy is required to remove electron from the valence shell

Question: 244

What is meant by mixture ? Give example.

Answer: 244

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When two or more elements or compounds mix up physically without any fixed ratio they form a mixture

Question: 245

Describe atIeast two necessary conditions for the formation of a covalent bond.

Answer: 245

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Iwo necessary conditions for the formation of covalent bond are: (.) The electronegativity difference between atoms must be less. So. that the shared pair of electrons is attracted by both the atoms equally. (i1) Maximum 3 to 6 electrons are present in their valence shells

Question: 246

Define standard atmosphere pressure and write its unit .

Answer: 246

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The pressure exerted by a mercury column of 760mm at sea level called standard atmospheric pressure

Question: 247

What is absolute temperature scale ?

Answer: 247

247-861

Lord kelvin introduced obsolute temperature scale or kelvin scale . The scale of temperature starts from 0K or -273.15°Cwhich is given as a name of absolute zero . It is the temperature at which an ideal gas would have zero volume

Question: 248

Write down the chemical formulas of the following

(a) Sugar (b) Sulphuric acid

Answer: 248

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(a) Sugar : C12H22O11

Question: 249

What id meant by atom and ion?

Answer: 249

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Atom

1- It is the smallest particle of an smallest particle of an element.

2- It is electricallyneutral

3- It can take part in a chemical reaction

Question: 250

Difference between true solution and colloid solution?

Answer: 250

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True solution:Solutions are the homogeneous mixture of two or more than two components.

Question: 251

Write two properties of ionic compound .

Answer: 251

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1: Ionic compound are mostly crystalline solid

Question: 252

Write down the name of particles which determine the mass of an electron .

Answer: 252

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The proton and neutron determine the mass of an atom

Question: 253

Write difference between homoatomic and heteroatomic molecules ?

Answer: 253

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Heteroatomic molecules:

The molecules consisting of different types of atoms are called heteroatomic molecules

Question: 254

Why the liquid molecules are mobile ?

Answer: 254

254-861

Liquid molecule have less intermolecular forces as compared to solids , which are not able to stable molecules of liquid at a fixed points . That is why liquid molecules are mobile

Question: 255

Define atomic number and atomic mass .

Answer: 255

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Atomic mass :

1: The sum of number of protons and neutrons present in the nucleus of an atom is called atomic mass

2: It is represented by A

Example : Atomic mass of carbon is 12

Question: 256

Write down any two properties of metals .

Answer: 256

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1: They show metallic luster

Question: 257

Write any two properties of covalent compounds .

Answer: 257

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1: Properties of coordinate covalent compounds are similar to those of covalent compounds . They are unsoluble in water and don't ionize so make solution on solving in organic solvent

Question: 258

What is difference between elements and compound ?

Answer: 258

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Compound : Compound is a substance made up of two or more elements chemically combined together in a fixed ratio by mass

Example : Water (H2O)

Question: 259

Why does sodium lose one electron and attain +1 charge?

Answer: 259

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Sodium has one electron in its valence shell. So. it loses its outer most electrons to complete its octet and become positive ion .i.e. Na⁺

Question: 260

What is the difference between the evaporation and boiling point ?

Answer: 260

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Evaporation : The process of changing of a liquid into a gas phase is called evaporation .

Question: 261

Why atomic number is more fundamental property to arrange elements than atomic mass?

Answer: 261

261-861

Due to two reasons :

1: It increase regularly from element to element

Question: 262

Which gasses are present in air ? Write their names .

Answer: 262

262-861

Oxygen , nitrogen , carbon dioxide , argon are major gasses present in air

Question: 263

Human body made up of how many elements ? Write their names .

Answer: 263

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Six elements constitute about 99% of our body mass , oxygen 65% , Carbon 18% , Hydrogen 10% , Nitrogen 3%, Calcium 1.5% and phosphorous 1.5% , Potassium , Sulphur , Magnesium and sodium constitute 0.8 % of our body mass . Wherease copper , zinc , chlorine , fluorine , iron , cobalt and magnesium constitute only 0.2% of our body mass

Question: 264

Which are physical properties of matter ?

Answer: 264

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1: Matter exists in three physical state i-e gas, liquid , and solid

Question: 265

What is charles law ? Write its equation .

Answer: 265

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French scientist J.Charles in 1787 , presented his law that states the volume of given mass of a gas is directly proportional to the absolute temperature if the pressure is kept constant

Question: 266

Write the percentage of volume by weight of oxygen in atmosphere and oceans

Answer: 266

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In atmosphere oxygen is 21% while in oceans it is 86%

Question: 267

How the properties of elements repeat after regular intervals?

Answer: 267

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The modern periodic table is based upon the arrangement of elements according to increasing atomic number. When the elements are arranged according to increasing atomic number from left to right in a horizontal row. properties of elements were found repeating after regular intervals

Question: 268

Describe difference between concentrated and dilute solution .

Answer: 268

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Concentrated solution : The solution which contains relatively large amount of dissolved solute in solution is called concentrated solution

Question: 269

Why does evaporation increases with the increase in temperature ?

Answer: 269

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Evaporation increase with the increase of temperature because at high temperature K.E of the molecules increase so high that they overcome the intermolecular forces and evaporate rapidly

Question: 270

Define empirical formula and give an examples .

Answer: 270

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Empirical formula: empirical formula is a formula which represents the simplest whole number ratio of atoms present in a compound

Question: 271

Write the simplest way to distinguish between solution and pure liquid .

Answer: 271

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The simplest way to distinguish between a solution and a pure liquid is evaporation . The liquid which evaporates completely , leaving no residue , is a pure compound , while a liquid which leaves behind a residue on evaporation is solution

Question: 272

Calculate the formulas mass of potassium sulphate

Answer: 272

272-861

Formulas mass of potassium sulphate (K2SO4)

K2SO4 = 2(39)+(32)+4(16)

= 78+32+64

= 174a.m.u

Question: 273

What is meant by malleability ?

Answer: 273

273-861

Malleabilityis the property by virtue of which a metal can be drawn into sheets

Question: 274

Write down the names of elements of groups 1 with their symbols .

Answer: 274

274-861

1st group elements are called alkali metals . It consists of hydrogen (H) , lithium (Li) , sodium (Na) , potassium (K) , rubidium (Rb) and cesium (Cs) , and francium (Fr)

Question: 275

Why metals are good conductor of electricity ?

Answer: 275

275-861

Metals are good conductors of heat and electricity in solid and liquid state due to mobile electrons

Question: 276

Who discovered proton and neutron ?

Answer: 276

276-861

Proton is discovered by Goldstein in 1886

Question: 277

Define pressure and write its unit .

Answer: 277

277-861

Pressure : It is defined as the force exerted by per unit surface area

Question: 278

Ionic compounds conduct electricity in solution or molten form. Why?

Answer: 278

278-861

Ionic compounds conduct electricity in solution or molten form because in these two states ionic compounds have free ions in them. When these free ion move in solution or molten gate they become conductor of electricity

Question: 279

For an element Z = 92 A = 238 Calculate number of neutron in it

Answer: 279

279-861

Atomic mass = No of protons + No of neutrons =A=238

No of protons Z = 92

No of neutrons =N=A-z

=238-92= 146

Question: 280

Explain any two factors that effect the diffusion .

Answer: 280

280-861

Factors effecting in diffusion :

1 :Size of molecules : Big sized molecules diffuse slowly

Question: 281

Define pascal .It is the unit of which quantity ?

Answer: 281

281-861

If one newton force is applied on 1m²area then pressure is called one pascal . It is unit of pressure

Question: 282

What are two defects in Rutherford's atomic model ?

Answer: 282

282-861

1: According to classical theory of radiation , electrons being the charged particles should release or emit energy continuously and they should ultimately fall into the nucleus

Question: 283

What is maximum capacity of a metal ?

Answer: 283

283-861

1: K shall can accommodate 2 electrons

Question: 284

Write two difference between molecule and molecular ions .

Answer: 284

284-861

Molecule :

1: molecule is formed by the combination of two or more atoms . Which can exist independently and shows all the properties of that compound i.e CO2, CH4 etc

2: It is always neutral

3: It is formed by the combination of atoms

4: It is stable unit

Question: 285

Define Dynamic equilibrium ?

Answer: 285

285-861

When the rate of evaporation becomes equal to rate of condensation . At that stage the number of molecules evaporating will be equal to the number of molecules coming back (condensing) to liquid . This state is called Dynamic equilibrium

Question: 286

What is the difference between diffusion and effusion ?

Answer: 286

286-861

Diffusion: The spontaneous mixing of molecules by random motion and collision of gases form homogenous mixture is called diffusion

Question: 287

Convert 560 torr into cmHg

Answer: 287

287-861

1 torr = 1mm Hg

Question: 288

What is kept constant in Charles law ?

Answer: 288

288-861

Pressure is kept constant in Charles law

Question: 289

Why big size covalent molecules have high melting and boiling points?

Answer: 289

289-861

Bigger molecules with three dimensional bonding form covalent crystals which are very stable and have high melting and boiling points.

Question: 290

Give some examples of arsenic and silver .

Answer: 290

290-861

Symbols of arsenic and silver are as following

Question: 291

Define Boyle's law .

Answer: 291

291-861

According to Boyle's law the volume of a given mass of a gas is inversely proportional to its pressure at constant temperature .

Question: 292

How many elements are in first period and what are their names and symbols?

Answer: 292

292-861

There are two elements in first period, hydrogen (H), helium(He)

Question: 293

Define molecular mass and give example .

Answer: 293

293-861

Molecular formula that shows actual number of atoms of each element present in molecules of that compound

Question: 294

Differentiate duplet and octet rule.

Answer: 294

294-861

Duplet Rule:

Attaining two electrons in valence called duplet rule.

Example. , Li⁺Hefollow duplet rule.

Question: 295

What is solid-solid solution ? Give two examples .

Answer: 295

295-861

Alloy: When solid solvent and solid solute make solutions it is called solid-solid solution

Question: 296

Define periods ?

Answer: 296

296-861

Seven horizontal rows present in periodic table are called periods . Numbered from 1 to 7

Question: 297

Write down electronic configuration of phosphorous .

Answer: 297

297-861

Atomic number of phosphorous is 15 Electronic configuration is given as below :

Question: 298

In which unit body temperature is measured ?

Answer: 298

298-861

Body temperature is measured in fahrenheit scale

Question: 299

Calculate molecular mass of sulphuric acid .

Answer: 299

299-861

Molecular mass of sulphuric acid H2SO4

=2(1)+(32)+4(16)

=98amu

Question: 300

Why does evaporation cause cooling ?

Answer: 300

300-861

When the high kinetic energy molecules evaporates from the surface of liquid , the temperature of the remaining molecules falls down . To compensate the energy decrease , the molecules absorb heat from surrounding falls down and we feel cooling

Question: 301

Is the Boyle's law applicable to liquid ? Give reason .

Answer: 301

301-861

No we can not apply Boyle's law to liquid because in them intermolecular distance is very less and they are highly incompressible so the effect of pressure does'nt effect much on liquids . That's why we can not apply Boyle's law to liquids

Question: 302

Convert 30°Cto kelvin temperature

Answer: 302

302-861

We know that

(T)K = (T)°C +273

by putting the values of C°=30° we have

(T)K = (30)°C +273

(T)K = (30+273)°C

(T)K = 303

Question: 303

Define atomic mass unit .

Answer: 303

303-861

One atomic mass unit is 1/12th of the ,ass of one atom of carbon 12 . When this atomic mass unit is expressed in gram , it is 1amu = 1.66*10-24 g

Question: 304

Define transition temperature . Give example .

Answer: 304

304-861

The temperature at which one allotropes changes into another is called is called transition temperature

Question: 305

What do you mean by delta sign and why it develop ?

Answer: 305

305-861

The delta sign indicates partial positive or partial negative charge that is developed due to unequal sharing of shared pair or bonded pair of electrons

Question: 306

Write down the electronic configuration of following

1: Na 2: Al

Answer: 306

306-861

1: Atomic number of Na 11

₁₁Na = 1s². 2s² . 2p⁶ . 3s¹

Question: 307

Differentiate between lone pair and bond pair of electron.

Answer: 307

307-861

Lone Pair

The non-bonded electron pair available on an atom. like the one lone pair is available on nitrogen in ammonia is called a lone pair

Question: 308

Why drops of rain fall downward?

Answer: 308

308-861

The density of liquid depends upon its mass and volume . Liquids are denser than gases because molecules of liquid are closely packed and the space between their molecules are negligible . As the liquid molecules have strong intermolecular forces hence they cannot expand freely and have a fixed volume . Like gases they cannot occupy all the available volume of the container that is the reason why densities of liquid are high

Question: 309

Define melting point ?

Answer: 309

309-861

The temperature at which the solid starts melting and exists in dynamic equilibrium with liquid state is called melting point

Question: 310

How do atoms follow octet rule?

Answer: 310

310-861

Atoms follow octet rule to have the noble gas electronic configuration. For this purpose atoms attain 8 electrons in the outermost shell either by sharing. by losing or by gaining electrons

Question: 311

Define Mendeleev's periodic table ?

Answer: 311

311-861

A Russian chemist arranged elements (63) discovered at that time according to increasing atomic mass . ' Properties of elements are periodic function of their atomic masses '

Question: 312

An element with A = 39 , Z = 19 .Calculate the number of electrons and protons in one atom of this element

Answer: 312

312-861

Atomic mass of an element = A = 39

Atomic number of element = Z = 19

As we know that atomic number is the number of protons present in the nucleus of an atom so , proton and electron always equal in any atom , that's why ,

Number of protons =19

Number of electrons = 19

Question: 313

What would be the number of moles in 9.0 gram carbon ?

Answer: 313

313-861

Number of moles of carbon = 9 g

Molar mass of carbon = 12 g

Number of moles = ?

Question: 314

Why volume of gas decreases with increase of pressure ?

Answer: 314

314-861

Volume of gas decreases with increase of pressure because of empty spaces between their molecules . When gases are compressed the molecules come closer to one another and occupy less volume as compared to the volume in uncompressed state .

Question: 315

What is difference between ion and free radical ?

Answer: 315

315-861

Free radicals :

1: These are the atoms that have odd number of electrons . They do not have any charge

2: They can exists in solutions as well as in air

3: They may form in the presence of light

Question: 316

In which form sulphur exists at I00°C?

Answer: 316

316-861

Sulphur exists in monoclinic form at 100"C because at room temperature sulphur exists in rhombic form. The transition temperature of sulphur is 96"C at which rhombic sulphur convened into monoclinic form.

Question: 317

What is meant by condensation ?

Answer: 317

317-861

The returns of the vapours into liquids state on cooling is called condensation

Question: 318

How does electron differ from a neutron ?

Answer: 318

318-861

Electron

1: Electrons have negative charge

2: The mass of the electron is 1940 times less than proton

Question: 319

Write two significance of chemical formula .

Answer: 319

319-861

1: it indicates the mass of the compound in amu or grams

Question: 320

Define atomic radius ?

Answer: 320

320-861

The half of the distance between the nuclei of the two bonded atoms referred as atomic radius

Question: 321

What are Dobereiner's triads ?

Answer: 321

321-861

A German chemist Dobereiner's observed relationship between atomic masses of several groups of three elements called triads . In triads the central and middle element had atomic mass average of the other two elements

Question: 322

Define super-saturated solution .

Answer: 322

322-861

The solution that is more concentrated than a saturated solution at a given temperature is known as super- saturated solution

Question: 323

What are Lanthanide and actinide series ?

Answer: 323

323-861

Due to space problem two series of elements are placed below periodic table

Question: 324

Write down electronic configuration of sodium .

Answer: 324

324-861

Electronic configuration of sodium

₁₁Na = 1s² , 2s² , 2p⁶ , 3s¹

Question: 325

What is ionic bond? Give an example.

Answer: 325

325-861

Definition: A chemical bond which is formed due to complete transfer of electron from one atom to another atom is called ionic bond.

Question: 326

What are two factors on which evaporation depends ?

Answer: 326

326-861

Surface area : Evaporation is a surface phenomenon . Greater is surface area greater is evaporation

Question: 327

Define carbondating .

Answer: 327

327-861

1: The radioactive isotopes are used to estimate the age of fossils like dead plants and animals and stones etc . The age determination of very old objects based on the half-lives of the radioactive isotopes is called radioactive isotopes is called radioactive-isotopes dating

Question: 328

Why the elements are called s and p block elements?

Answer: 328

328-861

The elements having their valence electrons in s and p sub shell called s and p blocks elements.

Question: 329

Write chemical formula of Aluminium sulphate and Calcium phosphate .

Answer: 329

329-861

Aluminium sulphate: Al2(SO4)

Question: 330

Convert -45°C to kelvin temperature .

Answer: 330

330-861

(T)K = (T)°C +273

(T)K = (-45)°C +273

(T)K = (-45+ 273)°C

(T)K = 228

Question: 331

Why do the bigger size atoms have more shielding effect?

Answer: 331

331-861

In bigger size atoms the number of inner shells and inner shell electrons increases hence the shielding effect in bigger size molecules also increases.

Question: 332

What is relative atomic mass ? How is it related to gram ?

Answer: 332

332-861

The relative atomic mass of an element is the average mass of an atoms of that element as compared to 1/ 12th the mass of an atom of carbon -12 isotope . Atomic mass unit is represent by amu and in grams 1amu =1.66*10-24g

Question: 333

What is the affect of temperature on vapour pressure ?

Answer: 333

333-861

By increasing temperature , vapour pressure increases and by decreasing temperature vapour pressure decreases

Question: 334

Differentiate between shell and sub shell and give example .

Answer: 334

334-861

Sub shell :

1: Every main energy level or shell which have sub energy level (s) or shell are called sub shell

2: They are represented by small letter s, p, and f

Question: 335

Why is the hold of nucleus over the outermost electrons in metal weak ?

Answer: 335

335-861

The hold of nucleus over the outermost electrons is weak because of large size atoms and greater number of shells in between nucleus and valence electrons . Furthermore ,because of low ionization potentials , metals have the tendency to to loose their outermost electrons easily

Question: 336

Calculate the molecular mass of the carbon dioxide .

Answer: 336

336-861

Molecular mass of the carbon dioxide

CO2 = 12+2 (16)

= 44amu

Question: 337

Define periodicity ?

Answer: 337

337-861

Properties of elements were found repeating after regular intervals in periodic table it is the periodicity

Question: 338

Define solution with example .

Answer: 338

338-861

A solution is a homogenous mixture of two or more substances . The boundaries of compounds can not be distinguished i-e solution exists as one phase

Question: 339

Whether the density of a gas decreases on cooling ?

Answer: 339

339-861

The density of gas increase by cooling because their volume decreases

Question: 340

What is the empirical formula of acetic acid ? Calculate its molecular mass.

Answer: 340

340-861

Empirical formula of acetic acid CH2O

Question: 341

Define transition element ?

Answer: 341

341-861

_{d block elements called transition element}

Question: 342

On which two factors vapour pressure of any liquid depends ?

Answer: 342

342-861

Vapour pressure of liquid depends upon following factors :

Question: 343

Why ionic compounds easily dissolve in water?

Answer: 343

343-861

They dissolve easily in water because water is a polar solvent and has high dielectric constant that weakens the attraction between ions.

Question: 344

Write chemical formula of caustic soda and washing soda .

Answer: 344

344-861

Caustic soda: NaOH

Question: 345

Which is the simplest form of matter?

Answer: 345

345-861

Gas is the simplest form of matter.

Question: 346

Why are the rates of diffusion in liquids slower than that of gases?

Answer: 346

346-861

In liquid molecules intermolecular forces are stronger than gases and there molecules are, closer to each other. Asa result rate of diffusion in liquids are slower than gases.

Question: 347

Write down the chemical formula of silicon dioxide and calcium chloride .

Answer: 347

347-861

Silicon dioxide SiO2

Question: 348

Define groups ?

Answer: 348

348-861

The vertical columns in periodic table are called groups . Numbered from 1 to 18

Question: 349

Describe the number of molecules in 9 g water.

Answer: 349

349-861

Volume of water = 9g

Question: 350

Why 2nd ionization energy of an elements is higher than first one?

Answer: 350

350-861

fins: energy required to remove an electron from isolated mono positive gaseous ion (M') is called second ionization energy. So more energy is required to remove second electron from a mono positive gaseous ion because there is more electrostatic force present between the nuclei and electron. M⁺➜M⁺²1e^-

Question: 351

Define freezing point ?

Answer: 351

351-861

The temperature at which liquid and solid coexist at dynamic equilibrium is called freezing point

Question: 352

What is a triple covalent bond, explain with an example?

Answer: 352

352-861

Ans: When each bonded atom contributes three electrons, three bond pairs are involved in bond formation. This type is called triple covalent bond. Three small lines are used to indicate these three pairs of electrons between those atoms in the molecules of such compounds. For example: Nt & C2H2 Formulas: N.N.H-C==C-H

Question: 353

Write electronic configuration of Chloride ion Cl^-

Answer: 353

353-861

Electronic configuration of Chloride ion

Question: 354

What is meant by ion ? Give example .

Answer: 354

354-861

Ion is an atom or group of atoms having a charge on it .

Question: 355

What is effective nuclear charge ?

Answer: 355

355-861

The valence electron of an atom experiences less nuclear change than that of actual charge , it is called effective nuclear charge or Z_eff

Question: 356

What is the reason for the difference between solutions, colloids and suspensions?

Answer: 356

356-861

Particles of solutions are so small that they can't scattered the rays of light, thus do not show Tyndall effect.

Particles of colloids scatter the path of light rays thus emitting the beam of light i.e. exhibit the Tyndall effect.

Particles of suspension are so big that light is blocked and difficult to pass

Question: 357

For what purpose P-32 and Sr - 90 are used .

Answer: 357

357-861

1: For the treatment of skin cancer , isotopes like P-32 and Sr-90 are used because they emit less penetrating beta radiations

Question: 358

What are elements in group 3 to 12 called ?elements are normal elements because their valence electrons lie in s and p sub shell

Answer: 358

358-861

Elements in group 3 to 12 elements are normal elements because their valence electrons lie in s and p sub shell

Question: 359

Differentiate between molecular mass and formula mass .

Answer: 359

359-861

Formula mass:

1:The sum of atomic masses of all the atoms present in one formula unit of a substance is called formula mass

2:Formula mass is related to ionic compound

Examples : NaCl = 23+36.5= 58.5 amu

Question: 360

What types of electron pairs make a molecule good donor ?

Answer: 360

360-861

The lone pair of electron make a molecule a good donor

Question: 361

Wrote the observations made by Rutherford .

Answer: 361

361-861

Observations made by Rutherford are as follows :

Question: 362

Define Triatomic molecule and polyatomic molecule

Answer: 362

362-861

Polyatomic molecule : The molecules which consists of many atoms calledpolyatomic molecule

Question: 363

Which form of Sulphur exists at room temperature?

Answer: 363

363-861

Rhombic (S₈) Sulphur exists at room temperature

Question: 364

How many members are in group 17, is there any liquid, what is its name?

Answer: 364

364-861

There arc five members in group 17 which are F,C1 .Br , I and At. Only one liquid element is present named as bromine Br).

Question: 365

Write down chemical formula of calcium phosphate and sodium chloride ..

Answer: 365

365-861

Chemical formula of calcium phosphate and sodium chloride is as fellows :

Question: 366

What is the reason of arranging elements in a group?

Answer: 366

366-861

The reason of arranging of elements in a groups, is that they have same electronic configuration and same properties so they form a family.

Question: 367

Give the characteristics properties of ionic compounds

Answer: 367

367-861

the characteristic properties of ionic compounds. %Its: Characteristic Properties of Ionic Compounds: (I) lanai compounds are mostly crystalline solids. In I Ionic compounds in solid state have negligible electrical conductance but they are good conductors in solution and in the molten form. It is due to presence of free inns in them. lilt) Ionic compounds have high melting and boiling point example. NaCI has M.P. 800°C and B.P. 1413°C. (iv) Ionic compounds dissolves in polar solvents. Like NaCI dissolves in water.

Question: 368

How much NaOH is required to prepare its 500cm³ of 0.4m solution?

Answer: 368

368-861

Molar mass of NaOH =40gmol^-3

Question: 369

Define the term allotropy ?

Answer: 369

369-861

Allotropy: The existence of an element in more than one forms in same physical state is called allotropy.

Question: 370

Define relative atomic mass.

Answer: 370

370-861

Relative atomic mass of an element is the average mass of an atom of that element as compared to 1/12th the mass of atom of carbon-12 isotopes

Question: 371

Metals arc good conductor of electricity. Why?

Answer: 371

371-861

Metals are good conductors of electricity because metals have free electrons which are mobile in nature. Spaces are present among the atoms. Mobile electrons can move freely in these spaces. (Fence, movement/flow of electrons is known as electricity that's why metals are good conductor of electricity.

Question: 372

How cation and anion is formed ?

Answer: 372

372-861

Cation is formed by the loss of one or more electrons

Question: 373

Why are the liquids mobile.

Answer: 373

373-861

Liquid molecules are in continuous state of motion. They possess high kinetic energy and have weak intermolecular forces than solids That's why liquids are mobile

Question: 374

Considering the electronic configuration of nitrogen atom, how many electrons are involved in bond formation and w hat type of covalent bond is formed?

Answer: 374

374-861

Electronic configuration of N is 1s².2s².2p³ Nitrogen has 5 electrons in its valence shell. Three electrons are involved in bond formation and triple covalent bond is formed.: N = N :

Question: 375

What is solid-liquid solution ? Explain with example .

Answer: 375

375-861

When a solid dissolves in liquid and form solution called solid-liquid solution . If sugar dissolve in water it will be called solid-liquid solution.

Question: 376

Define formula mass and formula unit .

Answer: 376

376-861

Formula unit : formula unit is defined as the simplest whole number ratio of ions ,as present in the ionic compounds

Question: 377

Why is the bond between an electropositive and an electronegative atom ionic in nature ?

Answer: 377

377-861

Because ionic bond is formed due to transfer of electron from one atom to another atom is called ionic bond. The elements of Group 1 and Group 2 being metals have the tendency to lose their electrons forming positively charged ions. Whereas non-metals of Group 15 to Group 17 have the tendency to pin or accept electrons. They are electronegative elements with high electron affinities.

Question: 378

Describe exothermic reaction with example .

Answer: 378

378-861

Exothermic reaction are those reactions in which heat is released. In theses reactions test tubes becomes hot . Aqueous solution of calcium oxide (CaO) , lithium sulphate Li₂SO₄and cerium sulphate Ce₂(SO₄) are examples of exothermic reactions

Question: 379

Calculate the formula mass of the nitric acid .

Answer: 379

379-861

HNO3 = 1+14+48

= 63amu

Question: 380

Differentiate between crystalline and amorphous solid .

Answer: 380

380-861

Crystalline solid : Solids in which particles are arranged in a definite three-dimensional pattern are called crystalline solid

Question: 381

For what purpose is U-235 used ?

Answer: 381

381-861

The radioactive isotopes are used to generate electricity by carrying out controlled nuclear fission reaction in nuclear reactions e.g U-235 is bombarded with slow moving neutrons . The uranium breaks to produce Barium - 139 and Krypton - 94 and three neutrons . A large amount of energy is released which is used to convert water into steam boilers . The steam drives the turbine to generate electricity . This is the peaceful use of atomic energy

Question: 382

What characteristics properties do the covalent compound have ?

Answer: 382

382-861

They have usually low melting and boiling points. (ii I Flicy are usually bad conductors of electricity. lit: I hey are usually insoluble in water. IR I Bigger molecules with three dimensional bonding form covalent crystals which are very stable and hard. They have high melting and boiling points.

Question: 383

What is meant by molecular ion ?

Answer: 383

383-861

When a molecule loses or gains one or more electron , it forms a molecular ion

Question: 384

What is difference between polar and non-polar covalent bonds, explain with one example of each?

Answer: 384

384-861

Polar Covalent Bonds Non-Polar Covalent Bonds

If the covalent bond is formed between two different types of atoms then bond pair of electrons will not be attracted equally by the bonded atoms. One of the atoms will attract the bond pair of electrons more strongly than the other one. They form polar covalent bond. For example: H⁺—F', H+—CI^-

Question: 385

What is difference between solution and mixture ?

Answer: 385

385-861

Solution : Homogenous mixture of two or more substance called solution

Question: 386

How will you test whenever given solution is colloidal solution or not?

Answer: 386

386-861

If the panicles scatter the path of light rays thus emitting the beam of light i.e exhibit the Tyndall effect than the given solution is colloid.

Question: 387

What is vapour pressure ?

Answer: 387

387-861

The pressure exerted by the vapour of a liquid at equilibrium with the liquid at a particular temperature is called vapour pressure of liquid

Question: 388

How many electrons will be in M shell of an atom having atomic no 15?

Answer: 388

388-861

Atomic number 15

K shall = 2 electrons

L shall = 8 electrons

M shall = 5 electrons

Question: 389

What is difference between cation and anion ?

Answer: 389

389-861

Cation: An atom or group of atoms having positive charge on it is called cation

Example : like Na , k

Question: 390

Why gases are compressible ?

Answer: 390

390-861

Gases are highly compressible due to empty spaces between their molecules . When the gases are compressed , then molecules come closer to one another and occupy less volume than in uncompressed state

Question: 391

Define avagadro's number

Answer: 391

391-861

Avagadro's number is a collection of6.02 × 10^{23 particles. It is represented by symbol 'NA'. Hence the6.02 × 10^{23 number of atoms , molecules or formula unit is called avagadro's number that is equal to 1 mole of respective substance}}

Question: 392

What is tyndall effect ? On which factor it depends ?

Answer: 392

392-861

Tydnall effect: The particles of colloids are big enough to scatter the beam of light . It is called tydnall effect

Question: 393

Why HCl has dipole-dipole forces of attraction?

Answer: 393

393-861

HCl has dipole-dipole forces of attraction. The unequal sharing of electrons between two different types of atoms make one end of molecule slightly positive and other end slightly negatively charged. As shared pair of electron is drawn towards more electronegative atom, it is partially negatively charged. as chlorine in hydrogen chloride. 'The other end automatically becomes partially positively charged.

Question: 394

How atoms accommodate 8 electrons in their valence shells?

Answer: 394

394-861

toms can accommodate 8 electrons in their valence shell in three.

1: By giving valence shell electrons

2:By gaining valence shell electrons

3:By sharing valence shell electrons with other atoms

Question: 395

Write two properties of crystalline solids .

Answer: 395

395-861

1: In crystalline solids particles are arranged in definite in definite pattern .

Question: 396

State John Dalton's atomic theory .

Answer: 396

396-861

Main points of John Dalton's atomic theory are given as follows

Question: 397

Why solid show rapidly ?

Answer: 397

397-861

The particles of solids are fixed at their position and are not mobile . Therefore they have rigid structure and definite shape .

Question: 398

How a covalent bond becomes polar?

Answer: 398

398-861

When a covalent bond is formed between two different atoms having different electronagetivity then the bond pair of electron will not be attracted equally by the bonded atoms as a result partial positive and negative charges appear on atoms and covalent bond becomes polar.

Question: 399

Define reduction .

Answer: 399

399-861

Reduction is defined as addition of hydrogen or removal of oxygen during a chemical reaction

Question: 400

Define molar solution and give example .

Answer: 400

400-861

When one mole of solute is solved on one dm3 of solvent in measuring flask then it is called one molar solution

Question: 401

Why noble gases are non-reactive?

Answer: 401

401-861

The noble gases do have 2 or 8 electrons in their valence shells. It means all the noble gases have their valence shells completely filled. Their atoms do not have vacant space in their valence, shell to accommodate extra electrons. Therefore noble gases do not gain. lose or share electrons. that's why they are non - reactive

Question: 402

Define diatomic molecule and give example .

Answer: 402

402-861

If a molecule consists of two atoms called diatomic molecule

Question: 403

What is difference between solution aqueous solution ?

Answer: 403

403-861

Solution : A solution is a homogenous mixture of two or more substance

Question: 404

Describe difference between Rutherford's theory and Bohr's atomic theory .

Answer: 404

404-861

Rutherford's atomic theory

1: It was based upon classical theory

2: Electrons revolve around the nucleus

3: Atoms should produce continuous spectrum

4: Atoms should collapse

Question: 405

How many atoms of hydrogen present in one mole of water ?

Answer: 405

405-861

One molecule of water is made up of two atoms of hydrogen and 1 atom of oxygen , hence 2×6.02×10²³.atoms of hydrogen and6.02×10^{23 atoms of oxygen constitute one mole of water}

Question: 406

Write the names of two allotropic forms of sulphur .

Answer: 406

406-861

The allotropic forms of sulphur are given below :

Question: 407

Write down the electronic configuration of fluorine and Neon

Answer: 407

407-861

Electronic configuration of fluorine:

₉F=1s² , 2s² , 2p⁴

Question: 408

What are SI units of atomic radius ?

Answer: 408

408-861

Pico meter (pm) =10^-12m

Question: 409

Differentiate between gram atomic mass and gram molecular mass .

Answer: 409

409-861

Gram atomic mass: The atomic mass of an element expressed in grams . It is called gram atomic mass

Question: 410

When a gas is allowed to expand, what will be its effect on its temperature?

Answer: 410

410-861

According to Charles' Law when gas is allowed to expand its temperature also increases.

Question: 411

What is meant by colloid ?

Answer: 411

411-861

The solutions in which the solute particles are larger than those solute particles present in true solution but not large enough to be seen with naked eye are called colloid solution . They show tyndal effect

Question: 412

What type of elements have tendency of sharing of electrons?

Answer: 412

412-861

If bond formation is between similar atoms or between the atoms that have comparable electronegativities. then the chemical bond formation is by sharing of electrons

Question: 413

What is meant by periodic function ?

Answer: 413

413-861

Repetition of properties due to increases of atomic number after regular intervals in the periodic table is called periodic function

Question: 414

Define allotropy and give examples .

Answer: 414

414-861

The existence of an element in more than one form in same physical state but different chemical properties is called allotropy .

Question: 415

Write two / four characteristics of cathode rays.

Answer: 415

415-861

1: Cathode rays travel perpendicular to the cathode surface

Question: 416

What type of solutions butter and smoke are ?

Answer: 416

416-861

Solution : Butter , smoke

Question: 417

Calculate the number of mole carbon in 84 gram of carbon .

Answer: 417

417-861

Mass of C = 84 gm

Molecular mass of C = 12 gm

Quantity of moles = 84/12

= 7 moles

Question: 418

What are cathode rays ? Who discovered it?

Answer: 418

418-861

In 1897 JJ Thomson discovered cathode rays

Question: 419

Why has water polar covalent bond ?

Answer: 419

419-861

Water has polar covalent bonds because there is a difference of electronegativity (1.3) between H and O atoms . There will be an unequal attraction for the bond pair of electron between H and O atoms . It will results in the preparation of polar covalent bond

Question: 420

Define aqueous solution . Write its components .

Answer: 420

420-861

The solution which is formed by dissolving substance in water is called an aqueous solution . Water in the solution always in large amount and are called solvents

Question: 421

Write the chemical formula of water and sugar.

Answer: 421

421-861

Water :C12H22O11

Question: 422

Why suspensions and solutions do not show Tyndall effect , while colloids do ?

Answer: 422

422-861

Suspensions and solutions do not show Tyndall effect because particles of solution are so small that can't be scatter the rays of light and particles of suspension are so big that light is blocked and difficult to pass . The colloids do show Tyndall effect because particles scatter the path of light rays thus emitting the beam of light i-e exhibit the Tyndall effect

Question: 423

If 16g of oxygen contains 1 mole of oxygen atom, calculate the mass of one atom of oxygen in grams .

Answer: 423

423-861

No of atoms in one mole =6.02×10²³

Question: 424

Why do the colloids show tydnall effect ?

Answer: 424

424-861

Colloids shows tyndall effect because the particles of

” colloids scatter the path of light rays due to large size.

Question: 425

What type of elements form metallic bond?

Answer: 425

425-861

Metals form metallic bond

Question: 426

Define aqueous solution

Answer: 426

426-861

The solution which is formed by dissolving a substance in water is called an aqueous solution

Question: 427

Write properties of Neutrons .

Answer: 427

427-861

Properties of neutrons particles are given below :

Question: 428

Why solution is considered mixture ?

Answer: 428

428-861

The chemical reaction did not take place between the components of solution and the components kept constant their properties . That's way solution is considered mixture .

Question: 429

What is the relationship between evaporation and boiling point of a liquid?

Answer: 429

429-861

Boiling Point: .lioiling point is defined as the temperature at which the vapour pressure of a liquid becomes equal to the atmospheric pressure or any external pressure". When a liquid is heated. its molecules gain energy. The number of molecules which have moo than average kinetic energy increases. More and more molecules becomes energetic enough u overcome the intermolecular forces. Due to this, rate of evaporation increases that results increase of vapour pressure until a stage reaches where the vapour pressure of a liquid become equal to atmospheric pressure. At this stage the liquid starts boiling

Question: 430

Write formulas of two ionic compounds which are soluble in water .

Answer: 430

430-861

The two ionic compound which are soluble in water are following

Question: 431

Write electronic configuration of Mg

Answer: 431

431-861

Atomic number of Mg 12

Question: 432

Define oxidation in terms of electrons and give an example .

Answer: 432

432-861

Oxidation : The loss of electron by an atom or ion is called oxidation

Question: 433

Why do atoms react ?

Answer: 433

433-861

It is an universal rule that everything in this world tends to become more stable . Atoms achieve stability by attaining electronic configuration of inert gases (He ,Ne ,or Ar ) . Having 2 or 8 electrons in the valence shell is sign of stability . Attaining two electrons in the valence shell is called duplet rule while attaining 8 electrons in the valence shell is called octet rule

Question: 434

What is the nature of charge on cathode ray ?

Answer: 434

434-861

Cathode rays are deflected toward positive plate in an electric field showing that they are negatively charged

Question: 435

How molar solution is prepared ?

Answer: 435

435-861

One molar solution is prepared by dissolving 1 mole of the solute in sufficient water to make the total volume of solution upto 1 dm³ in a measuring flask

Question: 436

Why dose ice float on water?

Answer: 436

436-861

lCe float on water due to hydrogen bonding. The density of ice is 0.917gcm^-3 at OT and of water is 1 gcm³ at 0°C. Due to this ice molecules expand and float on water

Question: 437

Write two difference between atom and anion

Answer: 437

437-861

Ion :

1: It is the simplest unit of ionic compound

2: It has net charge either negative or positive on it

Question: 438

Write short note on discovery of Neutron.

Answer: 438

438-861

Chadwick discovered Neutrons in 1932 . He bombarded alpha particles on Beryllium . He observed that the radiation of very high penetrating power were produced ( They can move through long distance in air ) .These radiations were called Neutron

Question: 439

Why does group 1 elements prefer to combine with group 17 elements.

Answer: 439

439-861

The elements of Group-1 being metals have the tendency to lose their valence electrons forming positively charged ions. Whereas non-metals of Group-17 have the tendency to gain or accept electrons. They are electronegative elements with high electron affinities. If atoms belonging to these two different group, metals and non-metals, are allowed to react. chemical bond is formed

Question: 440

Define unsaturated solution .

Answer: 440

440-861

The solution which have capacity to dissolve more amount of solute is called unsaturated solution

Question: 441

Why is BF³, electron deficient?

Answer: 441

441-861

In BF³ molecule, three valence electrons of boron atom pair up with three electrons, one from each of three fluorine atoms. the boron atom even after the sharing of electron, remain shortage of 2 electrons in its outer most shell

Question: 442

Name the element of 1st period of periodic table

Answer: 442

442-861

1st period consists only two elements hydrogen (H2|) and Helium ( He)

Question: 443

Why test tube becomes cold when KNO3 is dissolved in water ?

Answer: 443

443-861

The dissolution of KNO₃ in water is an endothermic process in which heat absorbed when KNO₃ dissolve in test tube it becomes cold

Question: 444

What is a plum pudding theory ?

Answer: 444

444-861

Thomson put forth his plum pudding theory . He postulated that atoms were solid structure of positively charge with tiny negative particle stuck inside . It is like plum in a pudding

Question: 445

Write difference between saturated solution and unsaturated solution .

Answer: 445

445-861

Saturated solution : The solution containing maximum amount of solute at a given temperature is called saturated solution

Question: 446

Why do atoms form chemical bonds?

Answer: 446

446-861

Atoms achieve stability by attaining electronic configuration of inert gases ns² or ns²,np⁶ Atoms combine with one another. which is called chemical bond.

Question: 447

For what purpose , Iodine-131 is used ?

Answer: 447

447-861

Isotopes of iodine I-131 is used to diagnose goiter in thyroid

Question: 448

Describe difference between true solution and colloid .

Answer: 448

448-861

True solution : True solutions are the mixture of homogenous mixture of two or more than two components . Each component is mixed in such a way that their individual identity not visible

Question: 449

Which type of electron are responsible for holding the atoms together in metals ?

Answer: 449

449-861

Nuclei of metal atoms appear submerged in sea of these free mobile electrons . These mobile electrons are responsible for holding the atoms of metals together forming a metallic bond

Question: 450

Why the density of a gas is measured in gdm^-3while that of a liquid is expressed in gcm^-3?

Answer: 450

450-861

The density of a gas is measured in gdm^-3while that of a liquid is expressed in gcm^-3because gases have large volume which is measured by large unit dm³while liquid has less volume so it is measured by small unit cm³

Question: 451

What is meant quantum ?

Answer: 451

451-861

Quantum means fixed energy . It is the smallest amount of energy that can be emitted or absorbed as electromagnetic radiation . Quanta is plural of quantum . In 1918 , Noble prize in physics was awarded to German physicist Max Planck ( 1858-1947) for work on the quantum theory

Question: 452

Define oxidation and reduction reaction .

Answer: 452

452-861

Oxidation: Oxidation is defined as addition of oxygen or removal of hydrogen or electron during a chemical reaction

Question: 453

Why does rate of diffusion increase with increase of temperature?

Answer: 453

453-861

Diffusion increases by increasing temperature because at high temperature the in termolecular forces become weak due to high kinetic energy of the molecules

Question: 454

Define Crystalline solids and give two examples .

Answer: 454

454-861

Solids in which particles are arranged in a definite three-dimensional pattern are called crystalline solids

Question: 455

Calculate the value of angular momentum of 1st orbit where mvr = nh/2π

Answer: 455

455-861

Let angular momentum (mvr) of first orbit is =mvr = nh/2π

Question: 456

Write two examples of gas into gas solution .

Answer: 456

456-861

1:Air

Question: 457

Why suspension does not form homogeneous mixture?

Answer: 457

457-861

sn, Particles remain un dissolved and from a heterogeneous mixture. Particles settle down after some times.

Question: 458

Define m0ole and give example .

Answer: 458

458-861

Atomic mass , molecular mass or formula mass of a substance expressed in grams is called a mole

Question: 459

Write the name of two non-polar solvents .

Answer: 459

459-861

Toluene and benzene aretwo non-polar solvents

Question: 460

How many blocks are present in periodic table ?

Answer: 460

460-861

There are4 presentin periodic table called s, p, d and f block

Question: 461

Differentiate saturated and unsaturated solution

Answer: 461

461-861

Saturated : A solution containing maximum amount of solute at a given temperature is called saturated solution

Question: 462

Write down the number and names of subshell in N-shell .

Answer: 462

462-861

Number of sub shell in N shell is 4 named as s ,p ,d and f

Question: 463

How much amount of KOH required to form 1 molar solution ?

Answer: 463

463-861

Concentration of solution = 1dm³

Molar mass of KOH = 39+16+1

= 56 mol

Question: 464

What is meant by true solution ?

Answer: 464

464-861

True solution are the homogeneous mixture of two or more than two components . Each components is mixed in such a way that their individual identity is not visible

Question: 465

Why do ionic compounds conduct electricity in solution or molten form?

Answer: 465

465-861

Ionic compounds are good conductor in solution and molten form due to the presence of free ions in them

Question: 466

Write down the two postulates of Bohr's atomic model .

Answer: 466

466-861

1: The hydrogen atom consists of a tiny nucleus and electrons are revolving in one of circular orbits of radius ' r ' around the nucleus

Question: 467

Why does true solutions not show Tyndall effects?

Answer: 467

467-861

True solutions not show Tyndall effectsbecause particle are so small that they can not scatter the the rays of light, thus do

not show tyndall effect.

Question: 468

Define Shielding effect.

Answer: 468

468-861

The force of attraction between the nucleus and valence electrons is reduced due to the presence of internal - sell electrons , This effect is called shielding effect

Question: 469

Define oxidation and give example .

Answer: 469

469-861

Oxidation reaction : The loss of electron by an atom or ion is called oxidation .

Question: 470

Give two examples of gas in liquid solution .

Answer: 470

470-861

1: Fog

Question: 471

Write the redox reaction taking place during the electroplating of chromium.

Answer: 471

471-861

Reaction at the electrodes are as Follows:

At anode 40H-➜2H₂O+O₂+4e^-

At cathode C⁺³3e^-➜Cr

Question: 472

An element has 5 electrons in M shell . Find its atomic number

Answer: 472

472-861

The element has 5 electrons in M shell has atomic number 15 and name of element is phosphorous

Question: 473

Where does most of the mass of an atom exists ?

Answer: 473

473-861

Most of the mass of an atom exists in its nucleus . The sum of masses of protons and neutrons is equal to atomic mas of an atom

Question: 474

Define redox reaction , Give an example .

Answer: 474

474-861

The reaction in which oxidation as well as reduction takes place at a time called redox reaction

Question: 475

How mass number of same elements are different ?

Answer: 475

475-861

Isotopes of an element have same number of protons and electrons but different number of neutrons . That's why isotopes of an element have different atomic masses . Although atomic number remains same

Question: 476

What type of solution fog and brass are?

Answer: 476

476-861

1: Fog is a solution of liquid solute in gas solvent

Question: 477

State Charles's law

Answer: 477

477-861

The volume of a given mass of a gas is directly proportional to the absolute temperature when pressure kept constant."

Question: 478

Write down the position of hydrogen in the periodic table

Answer: 478

478-861

First periodic starts from hydrogen due to one electron in its valence shell it lies in the first group and first period

Question: 479

Define solution ?

Answer: 479

479-861

A solution is homogenous mixture of two or more substances

Question: 480

Write electronic configuration of chlorine and carbon

Answer: 480

480-861

Electronic configuration of carbon : ¹² C₆= 1s² , 2s² , 2p²

Question: 481

What do you mean by malleability?

Answer: 481

481-861

Malleability is the property by virtue of which metals can be drawn into sheets.

Question: 482

How many sub shell are there in second sub shell ?

Answer: 482

482-861

In second sub shell 'L ' has two sub shells s and p

Question: 483

Give the electronic configuration of carbon atom.

Answer: 483

483-861

Atomic no. of carbon = Z= 6

No of electrons in carbon atom =Z=6

Electronic configuration of carbon atom=ls².2s²,2p²

Question: 484

Describe two characteristics of canal rays .

Answer: 484

484-861

1: Canal rays travel in straight line in direction opposite to the cathode rays and cast a sharp shadow of an opaque object if placed in their path

Question: 485

If repulsive forces dominate to attractive forces will a covalent bond form?

Answer: 485

485-861

If the repulsive forces dominate to attractive forces the covalent will not be formed. The covalent bond formed only when the attractive forces dominates over the repulsive forces.

Question: 486

Why Lanthanides an Actanides are placed separately below periodic table . Explain

Answer: 486

486-861

Because of space problem in periodic table two series of elements were placed separately below the normal periodic table to keep it in a manageable and presentable form . Since the two series start after Lanthanum (z=57) and Actinum (z=89) , so these two series of elements are named as Lanthanides and Actanides

Question: 487

Why does a dipole develop in a molecule ?

Answer: 487

487-861

The unequal sharing of electrons between two different types of atoms make one end of molecule slightly positive and other end slightly negatively charged . As shared pair of electron is drawn towards more electronegative atom , it is partially negatively charged . The other end automatically becomes partially positively charged

Question: 488

What is diffusion ? Explain with example ?

Answer: 488

488-861

Diffusion is defined as spontaneous mixing up of molecules by random motion and collisions to form a homogeneous mixture

Question: 489

What is difference between solute and solvent ?

Answer: 489

489-861

Solute : The component of the solution which is present in smaller quantity is called solute

Question: 490

Write electronic configuration of Sulphur .

Answer: 490

490-861

Electronic configuration of Sulphur :

Question: 491

What type of bond exists in ionic compound?

Answer: 491

491-861

Ionic bond exists in ionic compound.

Question: 492

Write electronic configuration of Neon and Berylium

Answer: 492

492-861

Atomic number of Neon 10

Question: 493

What do you mean by evaporation and how it is affected by surface area?

Answer: 493

493-861

Evaporation: The process changing of a liquid into a gas phase is called evaporation.

Surface Area:

Evaporation is a surface phenomenon. Greater is surface area. greater is evaporation and vice versa. For example, sometimes a saucer is used if tea is to cooled quickly. This is because evaporation from larger surface area if saucer is more than that from the small surface area of a as cup.

Question: 494

What are the elements arranged in group 3 to 12 called ?

Answer: 494

494-861

The groups 3 to 12 are called transition elements . In these elements 'd ' sub shell is in the process completion

Question: 495

Why chlorine can accept only 1 electron?

Answer: 495

495-861

Chlorine has seven electrons in its valence shell. Chlorine being an electronegative element has the tendency to gain only one electron. They attain electronic configuration to the nearest noble gas "Ar"

Question: 496

Differentiate between solute and solvent ?

Answer: 496

496-861

Solute : The component which is present in smaller quantity is called solutee.g : Salt in water , salt is solute

Question: 497

What is electronegativity ? Write its unit .

Answer: 497

497-861

The ability of an atom to attract the shared pair of electrons towards itself in a molecule is called electronegativity

Question: 498

What type of attractive forces exist between HCL molecules ?

Answer: 498

498-861

Dipole-dipole attractiveforces exist between HCL molecules.

Question: 499

Write electronic configuration of Boron .

Answer: 499

499-861

Atomic no of Boron 5

Question: 500

Define triads and law of octaves .

Answer: 500

500-861

Triads : The group of three elements called triads . In these groups central and middle element had atomic mass average of the other two element

Question: 501

Which electrons are involved in chemical bonding?

Answer: 501

501-861

Only valence shell electrons are involved in chemical bonding

Question: 502

How are elements are arranged in 4th period ?

Answer: 502

502-861

In fourth period 18 elements are arranged in the ascending order of their atomic number

Question: 503

What is transition temperature of sulphur?

Answer: 503

503-861

Its transition temperature is 96℃.

Question: 504

Why the electrons move freely in metals ?

Answer: 504

504-861

This is because the valence shell electrons loosely held by nucleus of an atom . There is the weak force of attraction present between nucleus and the mobile valence electrons . Therefore valence electrons move freely in metals

Question: 505

Why is melting point of a solid considered its 'identification' characteristics ?

Answer: 505

505-861

The melting point of a solid considered its identification because pure solids have a sharp and specific melting point , no other solid has same melting point

Question: 506

Write electronic configuration of Aluminuim .

Answer: 506

506-861

Atomic number of Aluminium is 13

₁₃Al = 1s², 2s², 2p⁶, 3s², 3p¹

Question: 507

Describe trend of shielding effect in periodic table .

Answer: 507

507-861

The shielding effect increase down the group in the periodic table . Because of this it is easy to take away electron in potassium (Z=19) than from sodium (Z=11) atoms . Similarly the shielding effect decrease in a period if we move from left to right

Question: 508

Why we stir paint thoroughly before using?

Answer: 508

508-861

We stir paints thoroughly before using because paints is suspension and suspension is heterogeneous mixture of un- dissolved particles which can be seen with naked eye and settle down alter sometime. We stir paints thoroughly so that particles suspend again

Question: 509

For what purpose C-14 is used ?

Answer: 509

509-861

Uses of C-14

Question: 510

Write two uses of isotopes

Answer: 510

510-861

1: In the field of medicine isotopes of iodine 131 are use for diagnose of goiter in thyroid gland

Question: 511

Why the ionic compounds have high melting and boiling points?

Answer: 511

511-861

Ionic compounds have high melting and boiling points. As ionic compounds are made up of positive and negative ions, there exist strong electrostatic forces of attraction between oppositely charged ions. So, a great amount of energy is required to break these forces

Question: 512

Why water is called universal solvent ?

Answer: 512

512-861

Water is called universal solvent because it dissolves almost all the solute particles present in the world

Question: 513

What is the nature of electrode used in electroplating of chromium?

Answer: 513

513-861

The object to be electroplated acts as cathode while anode is made of antimonial-lead.

Question: 514

What is absolute temperature scale?

Answer: 514

514-861

Lord Kelvin introduced absolute temperature scale or Kelvin scale • This scale of temperature starts from OK or -273.15°C which is given the name of absolute zero.

Question: 515

Define electrochemical cell . With the names of its types .

Answer: 515

515-861

Electrochemical cell is an energy storage device in which either a chemical reaction takes place by using electric current or chemical reaction produces electric current

Question: 516

Define electronic configuration . Also give example .

Answer: 516

516-861

The distribution of electrons around the nucleus in various shells and sub shells according to their increasing energy is called electronic configuration.

Question: 517

Write any four examples of colloidal solution .

Answer: 517

517-861

1: Starch

Question: 518

Write down uses of radioactive isotopes as traces for diagnosis and medicine .

Answer: 518

518-861

1: The radioactive isotopes are used as tracer to diagnose the presence of tumor inside the body

Question: 519

Give two examples of suspension .

Answer: 519

519-861

1: In suspension the undissolved particles are big enough to be seen with the naked eye

Question: 520

Why arc the densities of gases tower than that of liquids?

Answer: 520

520-861

Gases has e low density than liquids and solids. It is due to light mass and more volume occupied by the gas molecules.

Question: 521

What is difference between short period and ling period ?

Answer: 521

521-861

Short period : First period of periodic table is called short period . It consists of Hydrogen and Helium

Question: 522

What is absolute zero?

Answer: 522

522-861

It is the temperature at which an ideal gas would have zero volume.

Question: 523

What do you mean by induced dipole?

Answer: 523

523-861

The charges in one molecule creates charges in other molecules these charges are called induced dipole.

Question: 524

Define reduction on the basis of electron and give example .

Answer: 524

524-861

Reduction reaction : The gain of electrons by atom or ion is called reduction reaction .

Question: 525

Two hydrogen atoms combine to form molecules H2 while 'He' atom remains monatomic . Explain ?

Answer: 525

525-861

Two hydrogen atoms combine to form molecules H2 while 'He' atom remains monatomic because the outer most shell of hydrogen is incomplete . On the other hand outer most shell of He is complete

Question: 526

Is sign of (⁰) used on Kelvin?

Answer: 526

526-861

No. Degree sign (°) is used with Celsius scale not with Kelvin scale.

Question: 527

Why volume of a gas decreases with increase of pressure"

Answer: 527

527-861

The volume of a given mass of a gas is inversely proportional to the pressure if the temperature is kept constant' therefore while decreasing the volume of gas pressure will increase

Question: 528

How many neutrons are there in C-12 , C-13 ?

Answer: 528

528-861

1: C-12 has 06 neutrons

2: C-13 has 07 neutrons

Question: 529

Explain the law of flow of heat ?

Answer: 529

529-861

In winter atmospheric temperature falls lower than that of our body temperature . According to principle of heat flow out from our body and we feel cold . To control this outward flow of heat , we wear black and warm clothes . To maintain body temperature we use dry fruits tea, coffee and meats etc

Question: 530

Is the Boyle's law valid at very high temperature?

Answer: 530

530-861

No. Boyle's law is not valid at very high temperature

Question: 531

Why size of an atom decreases from left to right in the periodic table?

Answer: 531

531-861

When we move from left to right in a periodic atomic number increase yet the size of atoms decrease gradually . It is because with the increase of atomic number and nuclear charge

Question: 532

Why is the formula of solute necessary for calculation of the molarity of the solution ?

Answer: 532

532-861

Formula of solute is necessary for calculation of the molarity of the solution because molarity depends upon No. of moles of solute

Question: 533

In electroplating of chromium which salts is used as an electrolyte?

Answer: 533

533-861

In electroplating of chromium, Cr₂(SO₄)₃, is used as an electrolyte.

Question: 534

What is atomic number of Sulphur ? Write down its electronic configuration .

Answer: 534

534-861

Atomic number of Sulphur IS 16 .

Question: 535

What is difference between electron affinity and electron -negativity ?

Answer: 535

535-861

Electron affinity : Energy emitted due to the absorption of an electron in gaseous atom of an element is called electron affinity .

Question: 536

Why the rate of diffusion of gases is rapid than that of liquid ?

Answer: 536

536-861

The rate of diffusion of gases is rapid than that of liquid because the movement of gas molecule is rapid as compared to liquid , So due to random motion and collision gases diffuses rapidly

Question: 537

Define oxidizing and reducing agents with example .

Answer: 537

537-861

Oxidizing agent:

1: Oxidizing agent is the species that oxides a substance by taking electrons from it

2: The substance (atom or ion ) which is reduced itself by gaining electrons is also called oxidizing agent

Question: 538

Describe endothermic reaction with example .

Answer: 538

538-861

Endothermic reactions are those reactions in which heat is absorbed in theses reactions test tubes becomes cold

Question: 539

What is periodic law?

Answer: 539

539-861

In 1913, H. Moseley observed that atomic number instead of atomic mass should determine the position of elements in the periodic table and according the periodic law was amended as properties of elements are periodic function of their atomic numbers

Question: 540

How can you justify that milk is a colloid?

Answer: 540

540-861

Milk is a colloid . It can be justified on the basis of tyndall effect . Itsa solute particles are larger but not enough and can't seen by naked eye amd not settled down after long time and show tyndall effect , So milk is colloid

Question: 541

Convert the following. Ans: a) 70 cm lig to atm. b) 3.50atm to torr. c) 1.5 atm to Pa.

Answer: 541

541-861

70 cm Hg to atm

We know that

76 cm 11g= 1 atm

1 em = 1/76 atm

70 cm Hg = 1/76. 70atm

70 cm lig =0.92 atm

Question: 542

Why shielding effect of electron makes cation formation easy ?

Answer: 542

542-861

Shielding effect reduce the effective nuclear charge due to the nucleus thus the net force on the valence electrons decrease due to higher shielding effect . That is why the removal of valence electron become easy for cation formation

Question: 543

What are spontaneous and non- spontaneous reaction ? Differentiate them

Answer: 543

543-861

Spontaneous reaction : The reaction which proceed without any external assistance and heat are called spontaneous reaction .These reactions takes place in galvanic cells

Question: 544

Which allotropic form of carbon is stable at room temperature (25°C)?

Answer: 544

544-861

Graphite is more stable at room temperature

Question: 545

Define Mendeleev's periodic law .

Answer: 545

545-861

Mendeleev arranged the known elements (63) in the order of increasing atomic masses in the horizontal rows called periods . So that elements with similar properties were in the same vertical columns . This arrangement of elements was called periodic table . According toMendeleev's periodic law properties of the element are periodic function of their atomic masses

Question: 546

Write down atomic number of nitrogen and oxygen .

Answer: 546

546-861

The atomic no of N₂ is = 7

Question: 547

In electroplating of silver, from where Ag+ ions come and where they deposit?

Answer: 547

547-861

In electroplating of silver in the cell, the anode dissolves to produce Ag+ ions, that towards the cathode. At cathode they're discharged and deposited on the object e.g. spoon. chemical reaction can be represented as:

Question: 548

What is difference between group and period ?

Answer: 548

548-861

Group : The vertical columns present in periodic table are called groups .There are 18 groups present in the periodic table

Question: 549

Why is vapour pressure higher at high temperature?

Answer: 549

549-861

At high temperature, vapour pressure is higher than at low temperature. At elevated temperature, the Kinetic energy of the molecules increases enough to enable them to vaporize and exert pressure.

Question: 550

Why are dipole forces of attraction not found in halogen molecules?

Answer: 550

550-861

Dipole forces of attraction do not found in halogen molecules because they have same electronegativity and there is equal sharing of electrons.

Question: 551

Write two uses of redox reaction .

Answer: 551

551-861

Redox reaction are useful in batteries to produce energy and this electricity is used to drive non-spontaneous reaction

Question: 552

How does nature of attractive forces of solute-solute solvent -solvent affect the solubility?

Answer: 552

552-861

Solutions formation depends upon the relative strength of attractive forces between solute - solute , solvent-solvent and solute-solvent . Generally solutes are solids , ionic solids are arranged in such a regular pattern that the inter ionic forces are at a maximum . If the new forces between solute and solvent particles overcome the solute-solvent attractive forces , then solute dissolves and make a solution . If the forces between solute particles are strong enough then solute-solute forces , solute remains insoluble and solution is not formed

Question: 553

Write example of use of radioactive isotopes in the field of medicine and radiotherapy

Answer: 553

553-861

In the field of medicine isotopes of iodine I -131 are used for diagnosis of goiter in thyroid gland . While P-32 and Sr 90 are used in the field of radioactivity

Question: 554

Define standard atmospheric pressure . What are its units ? How it is relate to the pascal ?

Answer: 554

554-861

It is defined as the pressure exerted by a mercury column of 760 mm height at sea level

Question: 555

Define non polar covalent bond and give example .

Answer: 555

555-861

Non polar covalent bond is formed between two similar atoms the hsred pair of electrons is attracted by both the atom equally

Question: 556

Define hydrogen bonding ?

Answer: 556

556-861

Th partially positive charged hydrogen atom of one molecule attracts and forms a bond with partially negatively charged atom of the other molecule the bonding is called hydrogen bonding

Question: 557

Define Newland octaves law ?

Answer: 557

557-861

In 1864 British chemist Newlands put forward his observations in the form of law of octaves . He noted that there was a repetition in chemical properties of every eight element if they are arranged by their increasing atomic masses

Question: 558

Molecular formula of a sulphur molecule

Answer: 558

558-861

The Molecular formula of a sulphur molecule S₈

Question: 559

Can, you cool a gas by increasing its volume

Answer: 559

559-861

No. we cannot cool a gas by increasing its volume

Question: 560

What is the percentage m/volume ?

Answer: 560

560-861

It is the number of grams of solute dissolved in 100cm³of solution

Question: 561

^{Why magnesium is harder than sodium?}

Answer: 561

561-861

Magnesium is harder than sodium because in magnesium metallic bonding is stronger. While sodium is relatively soft metal due to weak metallic bonding in their atoms.

Question: 562

Why benzene is insoluble in water ?

Answer: 562

562-861

The principle of solubility is 'like dissolve like' . Benzene is a non-polar compound whereas water is a polar compound . Due to the reason , benzene is insoluble in water

Question: 563

Why does evaporation increase with the increase of temperature?

Answer: 563

563-861

At high temperature, rate of evaporation is high because at high temperature kinetic energy of molecules increases. So, it is high that they over-come the intermolecular forces and evaporate rapidly. For example, water level in a container with hot water decreases earlier than that of a container with cold water.

Question: 564

Why does sodium form a chemical bond with chlorine ?

Answer: 564

564-861

Sodium become Na by losing an electron and eight electrons remains in its valence shell . Chlorine gain an electron and becomes Cl^-ion . Both these ions attract each other and become stable

Question: 565

Which variables are kept constant in Charles' law?

Answer: 565

565-861

Pressure is kept constant in Charles' law

Question: 566

Explain Dobereiner's triads .

Answer: 566

566-861

Dobereiner observed relationship between atomic masses of several groups of three elements called triads . In these groups , the central or middle element had atomic mass average of the other two elements

Question: 567

What is an electron affinity ? Give an example .

Answer: 567

567-861

Trend in a group : In a group electron affinity values decreases from top to bottom because the size of an atom increases down the group . With the increase in size of atom shielding effect increase that results in poor attraction for the incoming electron i-e less energy is released out

Question: 568

What do you mean like dissolve like ? Explain with example ?

Answer: 568

568-861

The general principle of solubility is , like dissolve like

1: The ionic and polar substance are soluble in polar solvents . ionic solids and polar covalent compounds are soluble in water e.g KCl , Na₂CO₃, CuSO₄etc

Question: 569

Why HF is a weak acid ?

Answer: 569

569-861

HF is a weak acid because in HF -compound . There is strong intermolecular bonding . So, it does not readily ionize in water and release H+ in water the strong acid is that which is readily ionized in water but HF does not easily ionized in water

Question: 570

Why are the colloids quite stable ?

Answer: 570

570-861

In colloid particles are large but not large enough and they are stabilized hence they do not settle down for a ling time that is why colloids are quite stable

Question: 571

Which is lighter one aluminium or gold?

Answer: 571

571-861

Aluminum is lighter than gold because density or aluminium is 2.70 gcm'^-3 While of gold is 9.3 gcm^-3

Question: 572

Why amorphous solids do not have sharp melting points while crystalline solids do have ?

Answer: 572

572-861

Amorphous means shapeless . Solids in which the particles are not regularly arranged or their regular shapes are destroyed are called amorphous solids . They do not have sharp melting points . While solids in which particles are arranged in a definite three-dimensional pattern are called crystalline solids . They have definite surface or faces . Each face has definite angle with other . They have sharp melting points

Question: 573

Write down the position of hydrogen in the periodic table

Answer: 573

573-861

First periodic starts from hydrogen due to one electron in its valence shell it lies in the first group and first period

Question: 574

Why is white tin available at room temperature?

Answer: 574

574-861

White tin available at room temperature because it is stable at room temperature above 13.2°C

Question: 575

In which units body temperature is measured ?

Answer: 575

575-861

Body temperature is measured in Fahrenheit scales . Normal body temperature is 98.6°F , it is equivalent to 37° C . This temperature is close to average normal atmospheric temperature

Question: 576

What do you mean by malleable and ductile ?

Answer: 576

576-861

Malleability is the property by virtue of which metals can be drawn into sheets while ductility is the properties by virtue of which a metal can be drawn into wires

Question: 577

What is meant by ' Like dissolves like'

Answer: 577

577-861

1: The general principle of solubility is like dissolve like . The polar substance are soluble substances are soluble in polar solvents . Ionic solids and polar covalent compounds are soluble in water

Question: 578

Which of the following will scatter light and why?

Sugar solution, Soap solution, Milk of magnesia.

Answer: 578

578-861

Soap solution is colloidal solution and have particles large enough to scatter the light

Question: 579

Why suspension and solutions do not show Tyndnall effect , while colloids do?

Answer: 579

579-861

Solution does not show Tyndall effect because their particles are so small that they cannot scatter the ray of light . Suspensions do not show Tyndall effect because their particles are so big that light is blocked and difficult to pass . Colloid shows Tyndall effect because their particles are big enough to scatter the beam of light

Question: 580

Which isotopes are called radioactive isotopes ?

Answer: 580

580-861

The isotopes have ability to emit radiation naturally called radioactive isotopes

Question: 581

Calculate the oxidation number of chlorine in KClO₃ .

Answer: 581

581-861

{O.N of K } + {O.N of Cl } +3 {O.N of O } =0

{ +1 } + {O.N of Cl } +3 {-3} = 0

{O.N of Cl} + {1} +{-6} =0

{O.N of Cl } +1-6 =0

O.N of Cl {-5} =0

O.N OF Cl =5

Question: 582

What is general principle of solubility ?

Answer: 582

582-861

The general principle of solubility is ' like dissolve like ' . The polar substance dissolve in polar substance and non-polar substances and non-polar substances dissolve in non-polar substance

Question: 583

Classify the following into true solution and colloidal solution?

Answer: 583

583-861

Blood, Starch solution, glucose, tooth paste, copper sulphate, silver nitrate solution. Blood. Starch solution. tooth paste are the colloidal solution. Glucose solution. copper sulphate solution and silver nitrate solution are true solution.

Question: 584

What is the trend of electronegativity in the period ?

Answer: 584

584-861

The trend ofelectronegativity is same as of ionization energy and electron affinity . It increases in a period from left to right because higher Z_effshortens distance from the nucleus of the shared pair of electrons . This enhances the shared pair of electron

Question: 585

What do you mean by %volume/volume

Answer: 585

585-861

It is a volume in cm³ of a solute dissolved. per100cm3 of solution. For example 3O% alcohol solution means 30cm3 of alcohol dissolved in sufficient amount of water, so total volume would 100 cm³

Question: 586

Does Kelvin scale show negative temperature?

Answer: 586

586-861

No. Kelvin scale does not show a negative temperature

Question: 587

What are anode or cathode ?

Answer: 587

587-861

Anode : It is the electrode at which the oxidation takes place

Question: 588

Identify as colloids and suspensions : paints, jelly, soap solution , milk , milk of magnesia , chalk in water .

Answer: 588

588-861

Colloid : Soap solution , Milk , Jelly

Suspension : paints , milk of magnesia , chalk in water

Question: 589

Give difference between solution and colloids .

Answer: 589

589-861

Colloids :

The particles of colloids are large consisting of many atoms , ions , or molecules

Question: 590

Define noble gases and give example .

Answer: 590

590-861

Elements of group 18 are called Noble gases

All noble gases have completely filled outermost shells . This is because of this reason , they do not sow any chemical reactivity . They are chemically inert

Question: 591

What will happen if the pressure temperature is kept constant?

Answer: 591

591-861

The volume of gas will decrease three times when its pressure raised up to three times as temperature.

Question: 592

What is the half cell reactions occuring on cathode and anode in Daniel cell ?

Answer: 592

592-861

Following reactions occur at cathode and anode in Daniel cell .

Question: 593

Define molarity and write its equation .

Answer: 593

593-861

It is a concentration unit defined as number of moles of solute dissolved in one dm3 of solution . It is represented by M.

Question: 594

Define solubility ?

Answer: 594

594-861

The amount of solute in grams dissolved in 100g of solvent to prepare saturated solution at a particular temperature is called solubility of solute .

Question: 595

Why is HF a weak acid ?

Answer: 595

595-861

HF less ionizes , hydrogen bond is present between its molecules . That is why it is a weak acid

Question: 596

Write any two properties of solution and suspension

Answer: 596

596-861

Solution :

1: A solution is a homogeneous mixture of two or more substances

Question: 597

What happens to iron in the rusting process ?

Answer: 597

597-861

The oxidation of iron take place during rusting process and forms Fe₂O₃ . The chemical formula of rust is Fe₂O₃nH₂O

Question: 598

Why we stir paints thoroughlybefore use ?

Answer: 598

598-861

Paint is a suspension and there are undissolved particles in the suspension which are seen with naked eye . These particles settled down after some time .That's why we stir paints thoroughly before use

Question: 599

State whether allotropy is shown by elements or compounds or both ?

Answer: 599

599-861

Allotropy is only shown by elements . It is not a property of compounds

Question: 600

Why the boiling point of water higher than alcohol?

Answer: 600

600-861

Water has ability to form two hydrogen bonds while Ethyle alcohol has ability to form one hydrogen bond . That's why the boiling point of water is higher than alcohol

Question: 601

Define chemical bond and write names of its type .

Answer: 601

601-861

A chemical bond is defined as as a force of attraction between atoms that holds them together in a molecules . In other words , during bond formation there is some force which holds the atomic together

Question: 602

What is difference between valency and oxidation ?

Answer: 602

602-861

Valency : Valency is the combining capacity of an atom with other atoms . It depends upon the number of electrons in the outermost shell

Question: 603

What is the nature of electrode used in electroplating chromium ?

Answer: 603

603-861

During electroplating chromium the object to be electroplated act as cathode with anode is made up of antiamonial lead

Question: 604

Why ionization energy of Na is less than Mg?

Answer: 604

604-861

Ionization energy of Na is less than Mg because Na requires less energy to lose its valence electron than magnesium. Ionization energy is that energy, which is required to remove outermost electrons from the gaseous state of an element.

Question: 605

Give two characteristics of colloid .

Answer: 605

605-861

1: Colloid particles are large but can't be seen with naked eyes

Question: 606

Write any two rules for assigning oxidation number .

Answer: 606

606-861

1: The oxidation number (O.N) of an ion consisting on a single element is the same as the charge on that ion .

Question: 607

Which are long periods ? How many elements are present in long periods ?

Answer: 607

607-861

4th and 5th periods of the long firm of table are called long periods of periodic table . Both these periods consists on 18 elemensts present in each

Question: 608

Explain the effect of temperature on solubility .

Answer: 608

608-861

1: Temperature has major affect on the solubility of most of the substances

Question: 609

If we add 5cm3 of acetone in water to prepare to prepare 90cm3 of aqueous solution .Calculate the concentration (%v/v) of this solution .

Answer: 609

609-861

Using the relationship :

Question: 610

How can you justify that blood is a colloid?

Answer: 610

610-861

Blood appears to be a homogenous but actually it is a heterogeneous mixture. Blood particles do not settle down for a long time so we can say that blood is a colloidal solution

n

Question: 611

Which factor controls the non-metallic character of the element?

Answer: 611

611-861

The non - metallic character of elements is depending upon the electron affinity and electron affinity and electronegativity

Question: 612

Write down four important chemical properties of metals .

Answer: 612

612-861

1: Metals easily lose electron and form positive ions

Na➜ Na ⁺¹ +le^-

Question: 613

Name the metal which is the poorest conductor of heat ?

Answer: 613

613-861

Lead is the poorest conductor of heat

Question: 614

Name the by-products produced in Nelson's Cell?

Answer: 614

614-861

The chlorine and hydrogen gas are produce as by product in Nelson's Cell

Question: 615

Differentiate between ionic bond and covalent bond .

Answer: 615

615-861

Ionic Bond :

The type of chemical bond which is formed due to complete transfer of electron from one atom to another atom is called ionic bond

Question: 616

Why is naphthalene soluble in carbon tetrachloride and not in water ?

Answer: 616

616-861

Non -polar covalent substances are soluble in non-polar solvents due to this reason , naphthalene is soluble in carbon tetrachloride and not soluble in water because water is a polar solvent

Question: 617

Define oxidation in terms of oxygen with an example .

Answer: 617

617-861

Oxidation : The addition of oxygen in any chemical reaction is called oxidation reaction

Question: 618

Define electrolysis and give example .

Answer: 618

618-861

The decomposition of compound by passing electric current through molton or aqueous solution of the compound called electrolysis

Question: 619

What is difference between colloidal and suspension ?

Answer: 619

619-861

Colloid : The particles of colloid are large consisting of many atoms , ions or molecules . Particles are large but can't be seen with naked eye

Question: 620

How will you test weather given solution is colloidal solution or not ?

Answer: 620

620-861

Colloidal solution show tyndall effect and other solutions do not show tyndall effect

Question: 621

How many normal periods are and name also?

Answer: 621

621-861

2nd and 3rd periods are known as normal periods and they are two in number

Question: 622

Where sodium metal is obtained from fused sodium chloride .

Answer: 622

622-861

Sodium metal accumulates at iron cathode in down's cell

Question: 623

Write down names of two very reactive metals .

Answer: 623

623-861

1: Li (Lithium)

Question: 624

Why do suspensions not form the homogeneous mixture ?

Answer: 624

624-861

The force of attraction does not develop between particles of solvent and solute in the suspensions , due to this , suspension does not from homogeneous mixture

Question: 625

Write down use of paints and greases .

Answer: 625

625-861

1: Greasing or painting of the surface can prevent the corrosion of iron

Question: 626

Define effective nuclear charge .

Answer: 626

626-861

In an atom , attraction of outer most electrons around the nucleus is decreased due to inner electrons . In result , an atom faces less nucleus charge then the original

Question: 627

Why is the ionization energy of Na more than 'K'?

Answer: 627

627-861

The first ionization of Na (495,8kJ/mol ) is greater than first ioniztaion energy of 'K' (418.8kJ(mol) and the atomic size of Na is less than 'K' so the energy required to remove an electron from outermost shell of Na is greater than that ok K ,so the ionization energy of Na is more than k

Question: 628

Which salt is used as electrolyte in chromium electroplating ?

Answer: 628

628-861

In electroplating of chromium Sulphate Cr₂(SO₄)₃ is used an electrolyte

Question: 629

Differentiate between oxidation and reduction.

Answer: 629

629-861

Oxidation : Oxidation is defined as addition of oxygen or removal of hydrogen during a chemical reaction

e.g

ZnO + C➜Zn +CO₂

Question: 630

How many groups and period and periods are there in modern periodic table

Answer: 630

630-861

1: Long form of periodic table consists of seven horizontal rows called periods

Question: 631

Write two physical properties of sodium hydroxide .

Answer: 631

631-861

1: NaOH is crystalline solid at room temperature

Question: 632

Define electrochemistry .

Answer: 632

632-861

Electrochemistry is a branch of chemistry that deals with the relationship between electricity and chemical reaction

Question: 633

Define electrolyte . Give an example .

Answer: 633

633-861

Electrolyte : The substance which can conduct electricity in their solution or molten states are called electrolytes . Salts and acids are good electrolytes

Question: 634

Can colloids he separated by filtration, if not why?

Answer: 634

634-861

Colloids cannot be separated by filtration because particles are big but they can pass through a filter paper.

Question: 635

Differentiate between donor atom and acceptor atom.

Answer: 635

635-861

Donor atom : The atom which donates the electron pair in coordinate covalent bond is called donor atom

Question: 636

What is the colour of flame when sodium and calcium burn in air ?

Answer: 636

636-861

1: Sodium burns in air and produce golden yellow flame

Question: 637

What is meant by dipole dipole forces of attraction ?

Answer: 637

637-861

When partial positive and partial negative charges exists at different positions in a molecule , the adjacent molecules will arrange themselves in such a way that negative end of that molecule comes near to positive end of other molecule . It results in a net forces of attraction between oppositely charged ends of two adjacent molecules . These attractive forces are called dipole - dipole forces

Question: 638

What ammendment was made by H.Moseley in mendeleev periodic table ?

Answer: 638

638-861

According to mendleeve's periodic table properties of the element are periodic function of their atomic mass . Whereas according to H . Moseley's ammendments of periodic law properties of the elements are periodic function of their atomic numbers . This shows an atomic number of an element is equal to the number of electrons in a neutral atom . So atomic number provides the basis of electronic configuration as well .

Question: 639

What is electropositivity ? Explain with example

Answer: 639

639-861

Electropositivity : Metals have the tendency to loose their valence electron from their valence shell . The property of the metal is termed as electropositivity or metallic character

Question: 640

What are metalloids ? Give two examples .

Answer: 640

640-861

The elements whose properties are intermediate between metals and non-metals are called metalloids

Question: 641

Define polar covalent bond with example .

Answer: 641

641-861

Polar covalent bond is formed between two different atoms when the shared pair of electrons are not attracted equally by bonded atoms. The compounds resulting from covalent bond are called polar compounds

Question: 642

Which metal is used for metal work?

Answer: 642

642-861

As the metal work. means fire work. The metals are used in fire work due to its characteristic flame colour when they ignite in air . Na"- give golden colour, "Ca" give red colour etc.

Question: 643

Why is calcium more electropositive than magnesium ?

Answer: 643

643-861

Calcium is more electropositive than magnesium due to its large atomic size and less amount of ionization energy

Question: 644

Why do electrodes get their names "anode" and cathode in galvanic cell?

Answer: 644

644-861

In galvanic, cell. Oxidation take place at anode while reduction take place at cathode

Question: 645

Ice floats on the surface of water . Give reason.

Answer: 645

645-861

Floating of ice over water is because of hydrogen bonding . The density of ice at0°C (0.917gcm^-3) is less that of liquid water at0°C(1.00 gcm^-3) In the liquid state water molecules move randomly . However , when water freezes , the molecules arrange themselves in an ordered form , that gives them an open structure . This process expands the molecules , that results in ice being less dense as compared to water

Question: 646

Write down names of elements of first group and second period of the periodic table .

Answer: 646

646-861

First group of periodic table consists of hydrogen , lithium , sodium , potassium , rubidium , cesium , francium

Question: 647

What is the difference between steel and stainless steel ?

Answer: 647

647-861

Steel is a mixture while stainless steel is an alloy

Question: 648

Why elements are called s and p block elements ?

Answer: 648

648-861

Elements are called s and p block elementsbecause their last element is present in s and p sub shell

Question: 649

Write down the trend of atomic size in the periodic table.

Answer: 649

649-861

In period : Atomic size in a period from left to right decreases

Question: 650

Why calcium is more electropositive than to magnesium?

Answer: 650

650-861

Calcium is more Electropositivity than magnesium because metallic character or electroposltve character or electropositive character down the group increases due to loosely held and can be easily with drawn from their shells.

Question: 651

What is percentage-mass/mass(%m/m)?

Answer: 651

651-861

It is the number of grams of solute in 100 grams of solution

Question: 652

Why is 0₂ necessary for rusting?

Answer: 652

652-861

02 is necessary for rusting because it acts as oxidizing agent. It first oxidize iron-to Fe+2 ion thus Fe+ ion to rust (Fe₂0₃.n H₂O) in the presence of water.

Question: 653

What is difference between Mendeleev's periodic law and modern periodic law?

Answer: 653

653-861

Mendeleev's periodic law : The properties of elements are the periodic function of atomic masses

Question: 654

How oxygen react with group-2 metals?

Answer: 654

654-861

They are less reactive towards oxygen and oxides are formed on heating

Question: 655

Give the reason for the decrease of electronegatively in down the group .

Answer: 655

655-861

Electronegatively decreases down a group because size of the atom increases . The attraction for the shared pair of electrons weakens

Question: 656

What are electrolytic cell ?

Answer: 656

656-861

Electrolytic cell : The type of electrochemical cell in which the non-spontaneous chemical reaction is carried out with the help of electric current is called electrolytic cell

Question: 657

How platinum is used as a catalyst in automobiles and what are advantages of this use ?

Answer: 657

657-861

Platinum alloyed with palladium and rhodium is used as a catalyst in automobile as catalyst converter . It converts harmful gases into harmless gases

Question: 658

how can you explain the solute-solvent interaction to prepare NaCI Solution?

Answer: 658

658-861

When NaCI is added in water it dissolves readily because the attractive interaction between the ions of NaCI and polar molecules of water are strong enough to overcome the attractive forces between Na' and CI- ions in solid NaC1 crystal. In this process the positive end of the water dipole is oriented towards the CF ions and the negative end of water dipole is orwater molecules are so strong that they pull these ions from their positions in the the Na- ions. These ion dipole attractions between Na+ ions and water molecules, Cl- ions and water molecules are so strong that they pull these ions from their positions in the crystal and thus NaCl dissloves

Question: 659

Write the symbol of noble gasses

Answer: 659

659-861

1: Helium (He)

Question: 660

What is pacemaker ?

Answer: 660

660-861

A pacemaker is a small device in which body fluids act as an electrolyte . This device uses electrical pulses to prompt the heart to beat at a normal rate

Question: 661

Anode of downs cell is made up of non metal , what is its name ?

Answer: 661

661-861

Anode of down cell is made of non-metal , Its name is graphite . The Cl^-ions are oxidized to give Cl₂ gas at anode

Question: 662

How is the periodicity of properties depends upon the number of proton in an atom ?

Answer: 662

662-861

Periodicity of properties depends upon the atomic number . Atomic number is defined as total number of protons and nutron in a nucleus of any atom . That's the reason periodicity of properties depend upon protons

Question: 663

Why O2 is necessary for rusting ?

Answer: 663

663-861

Rusting is the oxidation of any metal . The important condition for rusting is moist air (air having water vapours formed which is called rust . In the absence of oxygen this reaction did not take place due to which rusting dis not happen

Question: 664

Determine the oxidation number of Mn in KMnO_4.

Answer: 664

664-861

{O.N k } + {O.N Mn } +4 {O.N O} =0

{+1} + {O.N Mn } +4 {-2 } =0

1+ {O.N Mn } 8=0

O.N Mn = 8-1

= 7

Question: 665

Name the best ductile and malleable metal ?

Answer: 665

665-861

Gold and silver

Question: 666

Name the elements of first group .

Answer: 666

666-861

1: Hydrogen (H)

Question: 667

What is the trend of ionization energy in the group ?

Answer: 667

667-861

As we move down the group , more and more shells lie between the valence shell and the nucleus of the atom , these additional shells reduce the electrostatic force felt by the electrons present in the outermost shell . Resultantly the valence shell electrons can be taken away easily . Therefore , ionization energy of elements decreases from top to bottom in a group

Question: 668

What do you know about the construction of an electrolytic cell?

Answer: 668

668-861

An electrolytic cell consists of solution of an electrolyte two electrodes (anode, cathode)that are dipped in the electrolytic solution and connected to the battery . The electrode connected to positive terminal is called anode and electrode connected to the negative terminal is called cathode

Question: 669

In electroplating of silver , from which electrolyte Ag+ comes and where they deposit ?

Answer: 669

669-861

In the electrolyte of silver (Ag)+ comes from anode and deposit on cathode .

Question: 670

Can pure gold be used for making ornaments ? If not , why ?

Answer: 670

670-861

Gold is too soft ,to be used as such . That is why it cannot be used aline in making ornaments . It is always alloyed with copper ,silver or some other metals

Question: 671

Write down two uses of gold .

Answer: 671

671-861

Because of its inertness in atmosphere , it is an ornamental metal as well as used in making coins . Gold is too soft to be used as such

It is always alloyed with copper, silver or some other metal

Question: 672

Difference between oxidation state and valency

Answer: 672

672-861

Oxidation : Oxidation state is apparent charged assign to an atom of an element in a molecule or an ion .

While assigning O.S the sign precedes the number

e.g +2

Question: 673

Write symbol of any four elements of halogen .

Answer: 673

673-861

1: Flourine (F)

Question: 674

Define Bond pair ?

Answer: 674

674-861

The valence electrons which take part in covalent bond is called bonding electrons . These electrons present in the incomplete valence shell

Question: 675

Write four physical properties of metals

Answer: 675

675-861

1: Almost all metals are solid (Except mercury)

Question: 676

What is by-products are produced in Down's cell?

Answer: 676

676-861

Chlorine is produce in the downs cell as a by product

Question: 677

Justify with an example the solubility of salt increases with increase in temperature?

Answer: 677

677-861

When salts like KNO3, KCl are added in water, the test tube become cold. It means during dissolution of this salts heat is absorbed. Such dissolving process in called endothermic Solvent + Solute + Heat-+Solution Solubility increase with the increase in temperature. It means that heat is required to break attractive forces b/w the ions of solute. This requirement is fulfilled by surrounding molecules.

Question: 678

What are non - electrolytes .Give one example

Answer: 678

678-861

The substances , which do not ionize in their aqueous solutions and do not allow the current to pass through their solutions are called non-electrolytes

Question: 679

Why does Aluminium not rust ? Explain

Answer: 679

679-861

Aluminium corrodes but it does not rust because a very hard material aluminium oxide , protects the aluminium from rust and further corrosion . Rust refers only to iron and steel corrosion . Whenever , iron corrodes its colour changes that exposes iron to further rusting

Question: 680

Why does covalent bond become polar?

Answer: 680

680-861

If the covalent bond is formed between two different atoms bond pair of electrons will not attracted equally by the bonded atoms . The atom which has greater electronegativity will attract bond pair more towards itself than other atom and hence molecule will become polar

Question: 681

Why the elements of group 13 to group 18 are called P block elements ?

Answer: 681

681-861

Elements of group 13 to 18 have their valence electrons in P subshell . Therefore , they are called as P-block elements

Question: 682

Write down the name of four least reactive metals .

Answer: 682

682-861

The names of least reactive metals are following

Question: 683

Define ionization energy .

Answer: 683

683-861

Ionization energy is the minimum amount of energy required to remove the most loosely bound electron from the valence shell of an isolated gaseous atom

Question: 684

In electroplating of silver , from which electrolyte Ag+ come or where they deposit ?

Answer: 684

684-861

In the electrolyte of silver (Ag+) comes from anode and deposit on cathode

Question: 685

What is the relationship between electro positivity and ionization energy ?

Answer: 685

685-861

Electronegativity depends upon the ionization energy which is in turn depends upon size and nuclear charge of the atom

Question: 686

Write ant two chemical properties of non-metals .

Answer: 686

686-861

1 : Non-metals usually do not react with water

2: They do not react with dilute acids because non-metals are itself electron acceptors

Question: 687

Which factors affect the non-metallic character ?

Answer: 687

687-861

Non-metallic character depends upon Electron affinity and electronegativity

Question: 688

Write names of any two noble metals

Answer: 688

688-861

1: Copper

Question: 689

What is redox reaction ?

Answer: 689

689-861

The reaction in which simultaneously oxidation and reduction takes place is called redox reaction

Question: 690

Why ionization energy decreases in a group from top to bottom ?

Answer: 690

690-861

When we move down the group in periodic table , more and more shells lie between the valence shell and nucleus of the atom , these additional shells reduce the electrostatic force felt by electrons present in the outermost shell . Resultantly the valence shell electrons can be taken away easily . Therefore , ionization energy of elements decreases from top to bottom in the groups

Question: 691

State the physical properties of sodium .

Answer: 691

691-861

1: Its melting point is 97°C

Question: 692

Name a metal which exists in liquid form? Ans: All metals exists in solid state, only mercury (Hg) is the metal which exist in liquid state

Answer: 692

692-861

All metals exists in solid state, only mercury (Hg) is the metal which exist in liquid state

Question: 693

What are trends of ionization energy in periodic table ?

Answer: 693

693-861

Ionization energy increases from left to right in the period while it decreases from to bottom in a group

Question: 694

Describes the trends of electropositivity in a period and in a group .

Answer: 694

694-861

Electropositive character increase down the group because size of atoms increase and nuclear charge decrease . Electropositive character decreases across the period from left to right because atomic size decrease and nuclear charge increase

Question: 695

Identify a strong and weak electrolyte among the following compound

CuSO₄, Ca (OH)₂ , HCL , HNO3

Answer: 695

695-861

Strong electrolyte :HCL ,HNO₃ AND CuSO₄ are strong electrolyte

Question: 696

Define shielding effect , Describe its trend in a period

Answer: 696

696-861

Shielding effect : The force of attraction between the nucleus and valence electrons is reduced due to the presence of internal - shell electrons (core electrons ) This is called shielding effect

Question: 697

Why atoms form bond ?

Answer: 697

697-861

It is universal rule that everything in this world tend to become more stable . Atoms achieve stability by attaining electronic configuration (ns² ,np⁶) like noble gases

Question: 698

Define oxidation state ?

Answer: 698

698-861

Oxidation state is the apparent charge assigned to an atom of an element in a molecule or ion

Question: 699

Write down names of any two moderate reactive metals

Answer: 699

699-861

1: Magnesium

Question: 700

Define Electrochemistry.?

Answer: 700

700-861

Electrochemistry is the branch of chemistry which deals with the relationship b-cl electricity and chemical reactions.

Question: 701

What is meant by atomic radius ? What is its unit ?

Answer: 701

701-861

The half of the distance between the nuclei of two of similar adjacent (bonded) atoms is called atomic radius

Question: 702

Identify strong or weak electrolyte among the following

CuSO₄ , H2CO₃ ,(OH)₂, AGNO₃ , Ca (OH)₂

Answer: 702

702-861

Strong electrolyte :HCL,HNO₃ and CuSO₄. AgNO₃ are strong electrolyte

Question: 703

iodine exists in solid state, can it be beaten with hammer to form sheets?

Answer: 703

703-861

No, only solid metals have the characteristic to be beaten with hammer to for sheet

Question: 704

Why silver and gold are least reactive ?

Answer: 704

704-861

From the transition metals of group 11 of periodic table Silover and Gold are least reactive because they do not lose electron easily

Question: 705

Why is galvanizing done?

Answer: 705

705-861

The process of coating a thin layer of zinc or iron is called galvanizing. Galvanizing is dot, because zinc protects the iron against corrosion even after the coating surface is broken.

Question: 706

Why elements of group 1 and group 2 are called S block elements?

Answer: 706

706-861

There are four blocks in the periodic table named after the name of the subshell which is in the process of completion by electrons .

Question: 707

Define electrolytes and electro chemical cell .

Answer: 707

707-861

Electrolytes : The substances , which can conduct electricity in their aqueous solution or molten state , are called electrolytes

Question: 708

Give application of silver ?

Answer: 708

708-861

1: Compound of silver are widely used in photographic films

Question: 709

What is the sign of stability of an atom ?

Answer: 709

709-861

The sign of stability of an atom IS achieving the electronic configuration similar to noble gases (He , Ne , or Ar etc) i-e (n² p⁶ ) or having two or eight electrons in their valence shell . In other words an atom is called stable if it follows duplet or octet rule

Question: 710

An element X has oxidation state 0 . What will be the oxidation state when it gains three electrons ?

Answer: 710

710-861

Suppose the element x

X0 +3e^-➜ X^-3

Question: 711

Why do ionic compound conduct electricity in solution form . Give reason

Answer: 711

711-861

Ionic compounds are found in the form of positive and negative ions when they are in solution or molten form . When these programs are connected through a battery their ions create an opportunity for an electron (charges) to move rapidly and current begins to flow Therefore , this flow of current proved that ionic compounds are good conductors and they conduct electricity in solutions or molten form

Question: 712

Why is 2nd ionization energy of magnesium very high than its 1st ionization energy

Answer: 712

712-861

Second ionization energy of magnesium is very high than its first ionization energy . Because it becomes very difficult to remove second electron from the Mg- ions as the nuclear charge attracts the remaining electrons strongly

Question: 713

Describe at least two necessary conditions for the formation of covalent bond .

Answer: 713

713-861

1: A covalent bond is formed between two non-metals

Question: 714

Calculate the oxidation number of Sulphur (S) in H₂SO₄

Answer: 714

714-861

H₂SO_{4 = 2(+1) +(S) +4(-2)}

_=2=S-8

_{S = +6}

Question: 715

Define brine ?

Answer: 715

715-861

The by-product in Nelson's cell are hydrogen gas (H₂) and chlorine gas (Cl₂)

Question: 716

Write two physical properties of non-metals.

Answer: 716

716-861

1: Non-metals have less melting and boiling point (except diamond)

2: They are generally soft (except diamond)

Question: 717

Give example of two polar compounds and give their chemical formula .

Answer: 717

717-861

Following are some examples of two polar compounds :

Question: 718

Why noble gases are not reactive ?

Answer: 718

718-861

The noble gases have 2 or 8 electrons in their valence shells i-e the valence shell of all the noble gases is complete . Their atoms do not have vacant space to accommodate extra electrons , So noble gases are not reactive

Question: 719

Define alloy and give example .

Answer: 719

719-861

Alloy : alloy is a homogeneous mixture of one metal with one or more metals or non-metals

Question: 720

Magnesium has electronic configuration 2,8,2 .Why magnesium tend to lose electron ?

Answer: 720

720-861

electronic configuration of magnesium is 2,8,2 . There are 2 electrons in its valence shell . It lose 2 electrons and get stable electronic configuration like noble gas Ne

Question: 721

Why ionization energies of alkaline earth metals are higher than alkali metals?

Answer: 721

721-861

Alkaline earth mewls have higher ionization energies than alkali metals because the electronic configuration of their valence shells is ns2. Their atoms are smaller and have more nuclear charge. That is why. they are reactive but less alkali metals

Question: 722

Why the trend of electron affinity and electron -negativity same in the period?

Answer: 722

722-861

The electron -negativity and electron affinity , both depends upon the size of atom and the nuclear charge . In the period from left to right the nuclear size decreases and nuclear charge increases . Therefore the trend of both is same

Question: 723

What is the reason of deficiency of electrons in BF_3?

Answer: 723

723-861

In the formation ofBF₃molecules , three valence electrons of boron (B) make three pairs of mutual coordination with three valance electrons from three fluorine atoms .. Despite of covalent bond made due to this mutual coordination , there is still deficiency of electron in boron . That's why octate is still incomplete (BF₃)

Question: 724

Give chemical reaction of methane with chlorine in bright light .

Answer: 724

724-861

In bright light (sun light) Cl2 react with CH4 violently and explosively

Chemical reaction : CH4 +2Cl2 ➜ C+4HCL

Question: 725

Why nitrogen is necessary for safety of life on earth ?

Answer: 725

725-861

Nitrigen is 78% in atmosphere and is necessary for safety of life on earth . It controls the fire and combustion process ,

otherwise all the things around us could burn with a single flame

Question: 726

Why the second ionization energy of magnesium is higher than than first ?

Answer: 726

726-861

Second ionization energy of magnesium is higher than than first , because it is very difficult to remove the second electron from the Mg⁺ ion due to much nuclear attraction . As a result of this attraction , size of ions decreases . Due to this reason , the second ionization energy of magnesium is higher than the first

Question: 727

Name a metal which can be cut with knife?

Answer: 727

727-861

Sodium is that metal which can be cut with knife, because it is soft.

Question: 728

Give chemical reaction between Methane (CH4) and chlorine (Cl2) in presence of diffused light .

Answer: 728

728-861

CH4 + Cl2 ➜ CH3Cl +HCL

CH3Cl +Cl2 ➜ CH2Cl2+HCL

CH2Cl2 + Cl2 ➜ CHCl2 +HCL

CHCL3 + Cl2 ➜ CCl4 ➜ CCl4 +HCL

Question: 729

What is difference between steel and stainless steel ?

Answer: 729

729-861

Steel : Alloy of iron with other metals called steel

Question: 730

Name the most abundant non- metal in earth's crust?

Answer: 730

730-861

Oxygen has has the highest percentage in earth's crust 47% and oceans 86% but second highest percentage in atmosphere 21%

Question: 731

What is meant by metallic bond ?

Answer: 731

731-861

When positively charged metal ions are held together by freely moving electrons , the bond which is formed called metallic bond

Question: 732

Why does atomic size increases in a group ?

Answer: 732

732-861

The size of atoms or their radii increases from top to bottom in a group . It is because a new shell of electrons is added up the successive period . Which the effect of nuclear charge

Question: 733

How is platinum used as a catalyst in automobiles and what are advantages of this use?

Answer: 733

733-861

An alloy of platinum. palladium and rhodium is used as catalyst in automobiles as catalytic converter. It converts most of the toxic gases (CO, NO2) being emitted by vehicles into less harmful carbon dioxide. nitrogen and water vapour.

Question: 734

Why the 2nd ionization energy is greater than 1st ionization energy ?

Answer: 734

734-861

Because after the removal of the first electron from the atom , its number of protons , become greater than electrons . The force of attraction between the nucleus and remaining valence shell electron increases . So more energy is required to remove the 2nd electron from the atom

Question: 735

Write the redox reaction taking place during the electroplating of chromium .

Answer: 735

735-861

Chromium sulphate Cr(SO₄)₃ used as an electrolyte in the electroplating of chromium that provides CCr⁺³ ions which reduce and deposit at cathode

Question: 736

Is triple covalent bond stronger than double covalent bond ? Give reason

Answer: 736

736-861

In triple covalent bond , three shared electron pair is involved while double covalent bond is formed between two shared electron pair . The greater number of shared pair electron , the bond will be stronger . That's why triple covalent bond is stronger than double covalent bond

Question: 737

Write down two significance of non-metals

Answer: 737

737-861

1: Non-metals are essential part of the body structure of all living things . Human body is made up of about 28 elements . But about 96% of the mass

of the human body is made up of just 4 elements i-e oxygen 65% carbon 18%, hydrogen 10% , and nitrogen 3% . Similarly plant bodies are made up of cellulose,

which is compose of carbon , hydrogen , and oxygen

Question: 738

What happens at cathode in galvanic cell ?

Answer: 738

738-861

Reduction process takes place at cathode in galvanic cell

Cu⁺²+ 2e➜ Cu

Question: 739

What is the trend of variation in densities of alkali metals?

Answer: 739

739-861

Densities of alkali metals increases down the group in the periodic table

Question: 740

Define single covalent bond and give one example .

Answer: 740

740-861

'When one electron is contributed by each bonded atom ,one bond pair is formed and it forms a single covalent bond '

Question: 741

Why an iron grill is painted frequently?

Answer: 741

741-861

Iron grill is painted frequently because due to presence of oxygen and water in air. It become, corrode. So to prevent it front rusting it is painted

Question: 742

Why does chlorine accept an electron and attain -1 charge ?

Answer: 742

742-861

Chlorine have seven electrons in its valence shell . It require one electron to complete its valence shell . That's why chlorine accept an electron and attain -1 charge

Question: 743

How chlorine chemical react with dilute ?

Answer: 743

743-861

Chlorine react withcold dilute NaCl to give sodium hypochlorite

2NaOH +Cl2 ➜ NaCl +NaOCL + H2O

Question: 744

Why does oxygen molecule not form a polar covalent bond ?

Answer: 744

744-861

In oxygen molecule formed by hydrogen and oxygen and hence there will be electronegativity difference between the oxygen and hydrogen . Due to which oxygen atlain negative and hydrogen atlain positive charge

Question: 745

What do you mean by 24 carat gold ?

Answer: 745

745-861

Purity of gold is shown by carat that indicates the number of parts by weight of gold that is present in 24 parts of alloy . Twenty four carat gold is pure and it means al the parts of alloy is gold

Question: 746

What is meant by octet rule ?

Answer: 746

746-861

Attaining 8 electrons in the outermost shell either by sharing by losing or gaining electrons is called octet rule . Atoms complete their octet by gaining , giving or sharing valence electrons with other atoms

Question: 747

What is meant by malleable and ductile metals ?

Answer: 747

747-861

Malleable : The substance that can be drawn into sheets are called malleable

Question: 748

What is the shape of cathode in the Nelson's cell ? Why is it perforated ?

Answer: 748

748-861

The cathode in Nelson's cell is U- shaped . It is perforated for the percolation of NaoH into a catch basin

Question: 749

What is the electronegativity of hydrogen and chlorine ?

Answer: 749

749-861

1: Value of electronegativity of hydrogen (H) is 22

Question: 750

Differentiate between polar and non polar covalent bond .

Answer: 750

750-861

Polar covalent bond : Covalent bond is formed between different atoms having different electronegativity between bonded atoms . Due to which one atom get negative and other get positive charge

Question: 751

Why electro positivity decreases from left to right in a period?

Answer: 751

751-861

Electropositivity decreases across the period from left to right. It means elements in the start of periodic are more metallic. This is because of two reasons,

(i) Size of atoms decreases.

(ii) Nuclear charges increases. upon nuclear charge. If nuclear charge increases the Electropositivity decreases because it becomes difficult to remove the electrons from outermost shell

Question: 752

What is galvanizing ?

Answer: 752

752-861

1: The process of coating a thin layer of zinc on iron is called galvanizing

Question: 753

State any four physical properties of metals.

Answer: 753

753-861

Physical Properties of Metals.

1: Almost all metals are solid except mercury.

2: Metals have high melting and boiling points. .

3:Metals possess metallic luster.

4: Malleable and ductile

Question: 754

Write down the reaction of magnesium with oxygen . How oxygen reacts with magnesium ?

Answer: 754

754-861

Magnesium reacts with oxygen and magnesium oxide is formed

Question: 755

Define the coordinate covalent bond? Explain with one example .

Answer: 755

755-861

Coordinate covalent bond or dative bonding is a type of covalent bonding in which the bond pair of electrons is donated by one bonded atom only . Coordinate covalent bond is also known as Dative covalent bond

Question: 756

Difference between substance and mixture.

Answer: 756

756-861

Substance: A piece of matter in pure form is termed as substance.

e.g. Glucose (C₆H₁₂O₆) Oxygen

Question: 757

How electro positivity depends upon size and nuclear charge of an atom?

Answer: 757

757-861

Electropositivity depends upon size and nuclear charge of an atom because when the size of atoms increases. Electropositivity increases as it becomes easier to lose electrons. It also depends upon nuclear charge if nuclear energy increase the electropositivity decreases because it becomes difficult to remove the electrons from outermost shell

Question: 758

An element in oxidation state +7 gains electrons to be reduced to oxidation state +2 . How

Answer: 758

758-861

Suppose an element X⁺⁷

Question: 759

Write two physical properties of magnesium .

Answer: 759

759-861

Magnesium is good conductor of heat and electricity

Question: 760

What is the nature of metal oxide?

Answer: 760

760-861

When metals react with oxygen they form metallic oxide, which are basic in nature. 2Mg+0₂➜2Mg0

Question: 761

Which is most precious metal ?

Answer: 761

761-861

The most precious metal is platinum

Question: 762

Define metallic character .

Answer: 762

762-861

The property of a metal to loose its valence electrons to form a positive ion is called metallic character

Question: 763

What do you mean by horticulture and how it is related agriculture ?

Answer: 763

763-861

It deals with the art of gardening . A horticulture works fir the betterment of existing varieties and for the production of new varieties of ornamental plants and fruits plants

Question: 764

Write two uses of calcium .

Answer: 764

764-861

1: It is used to remove sulphur from petroleum products

Question: 765

Write two properties of non-polar covalent compounds .

Answer: 765

765-861

1: They do not undergo charge separation

Question: 766

What do you means by 24 carat gold ?

Answer: 766

766-861

1: Purity of gold is show by carats .

Question: 767

What are electrolytes or non-electrolytes ?

Answer: 767

767-861

Electrolytes : The electrolytes which can conduct electricity in their aqueous solution of fuse form and produce more ions are called electrolytes

Question: 768

Why nitrogen forms compounds with alkaline earth metals directly ?

Answer: 768

768-861

A alkaline earth metals from stable nitrides when heated with nitrogen

Question: 769

Why sodium metal is more reactive than magnesium metal?

Answer: 769

769-861

Sodium metal is more reactive than magnesium metal because electro-positivity of met increase along the periods from left to right in periodic table. Element in the start of the period are more metallic or electropositive. Across the period from left to right size of atoms decreases due to increase in nuclear charge. That's why, sodium is more reactive than magnesium.

Question: 770

What is salt bridge ? What is its basic function ?

Answer: 770

770-861

Galvanic cell consists of two half cells, both these half cells are connected by salt bridge

Question: 771

Calculate the oxidation number of nitrogen in HNO₃ .

Answer: 771

771-861

HNO_{3 = (1) +(N) +3 (-2)}

_{= 1+N-6}

_{N = +5}

Question: 772

Can liquid and gases be brittle?

Answer: 772

772-861

No, Only solid non-metals are brittle.

Question: 773

What is difference between corrosion and rusting ?

Answer: 773

773-861

Corrosion : Corrosion is slow and continuous eating away a metal by the surrounding medium . It is a redox reaction which takes place on metals by the action of air and vapours

Question: 774

How will you compare he electropositivity ok alkali metals and alkaline earth metals ?

Answer: 774

774-861

:Alkali metal

These are highly electropositive. They have highly ionization energy values ranging from 520k.Jmol 1 for Li to 376 k.Jmol 1 for CS

Alkaline earth metal :They have less ionization energy values ranging from 1787k.Jmol 1 for Be to 936 k.Jmol 1 for Ba

Question: 775

Why oxygen is called non-metal?

Answer: 775

775-861

Non-metals form negative ions by gaining electrons. Oxygen atoms can accept 2 electrons therefore its valency is 2. 0+2e^-➜0^-2

Question: 776

Give uses of platinum

Answer: 776

776-861

Uses of platinum :

1: Platinum is used in hard disk coating and in maufacturing fibre optic cables

Question: 777

Why silver and gold are least reactive?

Answer: 777

777-861

Silver and gold are least reactive because these metals do not lose their electrons easily. They do not have the tendency to make cations and due to their soft nature. They cannot be used as such.

Question: 778

What is meant by electroplating ?

Answer: 778

778-861

Electroplating is depositing of one metal over the other by means of electrolysis

Question: 779

Why is gold used to make jewelry?

Answer: 779

779-861

Gold is very nonreactive or inert metal. It is not affected by atmosphere. It is not affected by any single mineral acid or base. It is most malleable and ductile of all the metals. Due these reasons the gold is used to make jewelry.

Question: 780

Why the ionization energy of Na is more than K?

Answer: 780

780-861

Ionization energy of sodium is more than K because down the group electropositive character increases and ionization energy decreases. As it become easier to remove electron' down the group

Question: 781

Why is platinum is used to make jewelry ?

Answer: 781

781-861

Platinum is used to make jewelry items because of its unique characteristics like colour , beauty , strength, flexibility and resistance to tarnish . It provides a secure setting for diamonds and other gemstone , enhancing their brilliance

Question: 782

Why ionization energy of Na is less than Mg ?

Answer: 782

782-861

Ionization energy of Na is less than Mg because Mg has greater nuclear charge than Na and also have smaller size

Question: 783

Write uses of silver .

Answer: 783

783-861

1: Being very sift metal , it is rarely used as such . Alloys of silver woth copper are widely used in making coins , silver-ware and ornaments

2: Compiunds of silver are widely used in photographic films and dental preparations

3: Silver also has important applications in mirror industry

Question: 784

What is galvanic cell? Give an example .

Answer: 784

784-861

The electrochemical cell in which a spontaneous chemical reaction takes place and generates electric current is called galvanic or voltaic cell

Question: 785

Define metal and give two examples .

Answer: 785

785-861

The elements which have ability to lose electron and forms cations called metals like Na , K , Ca

Question: 786

Which solution is used as an electrolyte in Nelson's cell ?

Answer: 786

786-861

In Nelson cell concentrated solution of sodium chloride is used . It is called brine solution

Question: 787

Why fluorine is more non-metallic than chlorine ?

Answer: 787

787-861

Fluorine is more reactive than chlorine because the electronegativity of fluorine is greater tahn chlorine

Question: 788

Why valence of chlorine is 1 ?

Answer: 788

788-861

The valency of chlorine is 1 and charge is negative because chlorine belongs to 17th group of periodic table . Its electronic configuration is Cl₁₇=1s²,2s²,2p⁶,3s²,3p⁵the valence shell of chlorine deficient by one electron . So, it accepts one electron from any metal and gets 1 charge

Question: 789

Why metallic character decrease along a period and increase in a group?

Answer: 789

789-861

Along the period: Metallic character decreases along the period from left to right.

Reason:

1:. From left to right size of atom decreases and nuclear charge increases so is difficult to remove electron and electropositivity decreases.

Question: 790

What is metallic coating ?

Answer: 790

790-861

For the protection against the rusting metals are coated with other metal and it is called metallic coating.

Question: 791

Write down the reaction occuring on cathode and anode during the electrolysis of water .

Answer: 791

791-861

Following reactions occur at anode and cathode during electrolysis of water

Question: 792

Complete the following chemical equation .

Answer: 792

792-861

NaO +H₂O➜ 2NaOH

Question: 793

Why alkali metals are more reactive than alkaline earth metals ?

Answer: 793

793-861

Alkali metals are extremely reactive because of their ns¹valence shell electronic configuration . As there is only one electron in their valence shell , it can be easily given out . It is the reason that they are always found in in nature as cations with +1oxidation state . Therefore , they readily form salts with non-metals

Question: 794

Write chemical reaction that takes place during working of Nelson's cell.

Answer: 794

794-861

Following reactions take place in Nelson's cell

Ions formed in Brine

2NaCl _(aq)➜ 2Na⁺ _(aq) +2Cl_(aq)

Question: 795

Differentiate between homoatomic and heteroatomic molecules with example.

Answer: 795

795-861

Homoatomic molecules; A molecule containing same type of atoms is called monatomic molecule.

for example: H₂, O₃, S₈

Question: 796

Describe the non-metallic character in groups and period of a periodic table

Answer: 796

796-861

Non-metallic charactyer in groups : In groups electrnegativity decreases from up to top bottom therefore non-metallic characrter alse decreases from top to bottom

Non-metallic charactyer in periods : In periods , electron affinity from left to right , due to which metallic character also increases

Due to this reason , fliorine is most non-metallic element in nature

Question: 797

What is difference between Duplet rule and octet rule ?

Answer: 797

797-861

Duplet rule : Attaining two electrons in the valence shell is called duplet rule

Question: 798

What is stainless steel?

Answer: 798

798-861

Stainless steel is an alloy which is formed by the combination of iron , ,chromium and nickel

Question: 799

hat is the importance of oxygen and carbon dioxide for plants and animals ?

Answer: 799

799-861

Life owes to non-metals as without O2 and CO2 those are essential gases for respiration of animals and plants respectively , life would not have been possible . In fact these

gases are essential for the existance of life

Question: 800

Why is ionization energy of sodium is less than magnesium ?

Answer: 800

800-861

Ionization energy of sodium is less than that of magnesium ,because it becomes very difficult to remove second electron from Mg+ ions as nuclear charge attracts the remaining electrons more strongly . In the result of this attraction size of the ion decreases, So all the elements of alkaline earth metals have high ionization energies as compared to alkali metals

Question: 801

Which force drives the non-spontaneous reaction to take place ?

Answer: 801

801-861

Non-spontaneous reactions are those which take place in the presence of an external agent . These reactions takes place in galvanic and electrolytic cells

Question: 802

Differentiate between molecular mass and formula mass, which of the following will be molecular formula?

Answer: 802

802-861

H₂O,NaCl, KI, H₂SO₄

Question: 803

Complete and balance the given chemical equation Na + H₂➜ ?

Answer: 803

803-861

2Na + H2➜ 2NaH

(Sodium ) (Hydrogen ) (sodium hydroxide )

Question: 804

How sodium metal is obtained from fused sodium chloride .

Answer: 804

804-861

On the industrial scale molten sodium metal is obtained by the electrolysis of fused NaCl in the Down's cell . This electrolytic cell is a circular furnace . In the center of the furnace there is a large block of graphite , which acts as an anode while cathode around it is made of iron

Question: 805

How electropositivity depends upon the nuclear charge of an atom ?

Answer: 805

805-861

Left to right in a period nuclear charge increase but the number of metals remains same thats whyleft to right there is continuous decrease in the size of atoms . Small size atoms have higher nuclear charge and thus have lower electropositivity . Large size atoms have lower nuclear charge so they have high electropositivity , so ability to liise electron is greater large sized atoms. In high nuclear charge it is difficult to lose electron . The electropositivity of elements depends upon the nuclear charge it is difficult to lose electron . The electropositivity of elements depends upon the nuclear charge

Question: 806

Which compounds of halogens are stable ?

Answer: 806

806-861

Halogens form very stable compounds with alkali metals

Question: 807

Differentiate between Lone pair and bond pair of electrons .

Answer: 807

807-861

Long pair : The pair of electrons which remain unshared during covalent bond formation is called long pair

Question: 808

Write two method for prevention of corrosion .

Answer: 808

808-861

Method for prevention of corrosion:

Following are some method from avoiding corrosion

Question: 809

Why the second ionization energy of magnesium is higher than the first one?

Answer: 809

809-861

he l ionization energy of magnesium is high but the 2" ionization energy of magnesium i, very high. It becomes very difficult to remove second electron from the Mg' ion as nuclear charge attracts the remaining electrons strongly. As a result of this attraction size of the ion decreases.

Question: 810

Write chemical reaction of water with bromine .

Answer: 810

810-861

bromine only reacts with water under following special condition .

Br2 + H2O ➜ HBr + HOBr

Question: 811

Which metals are the most malleable and ductile ?

Answer: 811

811-861

Gold (Au) is the most malleable and ductile of all metals . One gram of gold can be drawn into a wire of one and called ductile

Question: 812

Why covalent bond in H₂ is non-polar ?

Answer: 812

812-861

In H2 covalent bond is formed between two similar atoms , the shared pair of electron is attracted by both atoms equally , so non-polar covalent bond exist between hydrogen atoms

Question: 813

Complete and balance the following equation Mg +N₂➜ ?

Answer: 813

813-861

3Mg +N₂➜ Mg₃N₂

_{(Magnesium ) (Nitrogen) (Magnesium nitride)}

Question: 814

What are weak electrolytes? . Give example .

Answer: 814

814-861

The substances which ionize to a small extent when dissolved in water and could not produce more ions are called weak electrolytes

Question: 815

How electroplating of zinc is carried out ?

Answer: 815

815-861

The target metal is cleaned in alkaline detergent type solutions , and it is treated with acid , in order to remove any rust or surface scales. Next the zinc is deposited on the metal by immersing it in a chemical bath containing electrolyte zinc sulphate . A current is applied , which results in zinc being deposited on the target metal i-e cathode

Question: 816

6: Complete the following chemical equation :

1: Ca + H2 ➜ , 2: Ca + Cl2

Answer: 816

816-861

Calcium reacts with hydrogen at high temperature of form hydrides

1: Ca +H2 ➜ CaH2

Question: 817

Where do electrons flow from Zn electrode in Daniel's cell ?

Answer: 817

817-861

In Daniel's cell electron flow from Zn electrode to Cu electrode i-e from anode to cathode through external circuit

Question: 818

Can pure gold be used for making ornaments?If not why?

Answer: 818

818-861

No. pure gold cannot be used for making ornaments.

because gold is too sift to be used as such It is always alloyed with copper. silver and some other metals

Question: 819

Define corrosion ?

Answer: 819

819-861

Corrosion is slow and continuous eating away a metal by the surrounding medium . It is a redox chemical reaction that takes place by the action of air and moisture with metals

Question: 820

What are metalloides ? Gibe two examples

Answer: 820

820-861

The elements have characteristics of both metals and non-metals are called metalloids

Question: 821

Which metal is used for the galvanizing of iron ?

Answer: 821

821-861

Zinc metal is used for galvanizing of iron because it protects from corrosion

Question: 822

Why does reactivity of metals increase down the group?

Answer: 822

822-861

The reactivity of metals increase down the group due to increase in atomic size and shielding effect down the group . The ability of the metals to loose electrons increase down the group and ionization energy also decrease hence their reactivity increase down the group

Question: 823

Write the names of noble metals .

Answer: 823

823-861

The metals which give least reactions are called noble metals

Question: 824

Why silver is not used in pure form ?

Answer: 824

824-861

Silver is a very soft metal that's why it is not used as such in pure

Question: 825

Write any two uses of sodium .

Answer: 825

825-861

1:Sodium potassium alloy is used as a coolant in nuclear reactor

Question: 826

Write four physical properties of calcium metals .

Answer: 826

826-861

1: Calcium is silvery grey and fairly harder metal

Question: 827

What is the principle of electroplating ?

Answer: 827

827-861

Principle of electroplating is to establish an electrolytic cell in which anode is made of the metal to be deposited and cathode of the object on which metal is to deposit . The electrolyte is an aqueous solution of salt of the respective metal

Question: 828

How can we distinguish a metal from non-metal by a simple physical method ?

Answer: 828

828-861

Metals : On heating metals usually become soft and flexible

They are difficult to cut

Question: 829

Why copper is used for making electrical wires ?

Answer: 829

829-861

Copper is used for making electrical wires because it is highly ductile and least reactive . Copper is among noble metals

Question: 830

WHat do you know about the oxidizing characteristics of halogens ?

Answer: 830

830-861

Chlorine is the most poweful oxidizing agent. Oxidizing property of halogens is decreased from top to bottom . All halogens react with hydrogen gbas in the

presence of light and catalyst to make halides . Stability of their hydrogen halides are given below

HF > HCL > HBR > HI

Question: 831

Metals are good conductors of electricity .Why ?

Answer: 831

831-861

Metals have free moving electrons called mobile electrons . Due to presence of these electrons metals are good conductors of electricity

Question: 832

Why ionization energy ok alkaline earth metals is higher than alkali metals?

Answer: 832

832-861

The size of alkali metals is samaller than alkaline earth metals that's why they have high ionization energy

Question: 833

Define biotechnology?

Answer: 833

833-861

It deals practical of living organism to make substances for the welfare of mankind

Question: 834

Write uses of magnesium .

Answer: 834

834-861

1: Magnesium is used in flash light bulbs and in fireworks .

Question: 835

Write two properties of platinum.

Answer: 835

835-861

1: Platinum is a noble metal and very least reactive

Question: 836

What are difference between string and weak electrolytes .

Answer: 836

836-861

Strong electrolyte : The substance which ionizes completely in solution to produce more ions which can conduct strongly is called strong electrolyte

Question: 837

Write down melting point and boiling point of sodium metal .

Answer: 837

837-861

Melting and boiling point of sodium metal are as follows

Question: 838

Write two properties of silver

Answer: 838

838-861

1: Silver is a white Lustrous metal

2: Silver is good conductor of heat and electricity

3: Silver is a very malleable and ductile

Question: 839

Write difference between electrolytic cell and galvanic cell.

Answer: 839

839-861

Electrolytic cell :

1: It consists of one complete cell. connected to battery

2: Anode has positive charge while cathode have negative charge

3: Electrical energy is converted into chemical energy

4: Current is used for the non-spontaneous chemical reaction to take place

Question: 840

Compare two physical properties of metals and non-metals .

Answer: 840

840-861

Metal :

1:Almost all metals are solid (except mercury) they have high densities

Question: 841

Write down names of any four halogens .

Answer: 841

841-861

1: Fluorine 2: Chlorine 3: Bromine 4: Iodine

Question: 842

What does mean rusting of iron ?

Answer: 842

842-861

Corrosion of iron is called rusting . The important condition for rusting is moist air

Question: 843

Describe the chemical reaction of alkaline earth metals with hydrogen .

Answer: 843

843-861

Alkaline metals :

Reaction with oxygen :

1: Alkaline metals immediately tarnish in air giving their oxides which form strong alkalies in water

4Na +O➜ 2Na2 O

Na₂ O➜ 2NaOH

2: Reaction with hydrogen :

The form ionic hydrides with H₂at high temperature

2Na +H₂➜2NaH

Reaction with Halogens :

3: They react violently with halogens at room temperature to give halides

2Na +Cl₂➜ 2NaCL

Question: 844

Define halogens . give example .

Answer: 844

844-861

Halogens : The element of group 17 called halogens

Example : Chlorine , Fluorine , Bromine etc

Question: 845

How metallic character is changes in a group of periodic table ?

Answer: 845

845-861

Metallic character increase in a group from top to bottom due to increase in the size of atoms

Question: 846

How iron is prevented from rust by tin coating ?

Answer: 846

846-861

1:It involves the dipping of the clean sheet of iron in a bath of molten tin and then passing it through hot rollers

Question: 847

What is the significance of water for survival of life .

Answer: 847

847-861

Water is an essential compound for the survival of all the living things . It is made up of non-metals .It is not only the major part by mass of the bodies

of living things but it is also essenhtial to maintain the life . We can survive without water for days but not for a long period . Its shortage may cause death

Question: 848

Write down two properties of gold

Answer: 848

848-861

1: Gold is a yellow sift metal

2: It is most malleable and ductile of all the metals

Question: 849

Give chemical reaction of H₂ and Cl₂ and l₂Reaction of H₂ with Cl₂ :

Answer: 849

849-861

H2 reacts with Cl2 only in the presence of sunlight

H₂ + Cl₂ ➜ 2HCL

Question: 850

Why alkali metals are extremenly reactive ?

Answer: 850

850-861

Alkali metals : The elements in the first group of the periodic table are calleed alkali metals

Reactive of alkali metals :

Alkali metals are extrmely reactive elements because of their ns 1 valence shell electronic configuration . These metals only have one electronin theor valence shell , which can be easily

given out

Question: 851

Why do non-metals accept electron readily ?

Answer: 851

851-861

Non-metals have high electronegativity , can accept electrons readily in order to complete their last (valence ) shells

Question: 852

How galvanizing of iron sheets is done ?

Answer: 852

852-861

The process of Galvanizing is carried out by dipping a clean iron sheet in a zinc chloride bath and then heating it . After this iron sheet is removed , rolled into molten zinc metal bath and finally air -cooled . Advantages of galvanizing is that zinc protects the iron against corrosion

Question: 853

Why platinum is used as for making jewellery ?

Answer: 853

853-861

Platinum is very important metal . It is rust free and nin-reactive with oxygen and other gases which are present in atmosphere . Platinum is used to make .

jewellery items because of its unique properties like colour , beauty , strenght , flexibilty and resistance to tarnish

Question: 854

In what conditions H2 reacts with l2 ? Give equation of the reaction .

Answer: 854

854-861

H2 reacts with l2 on heating and in the presence of catalyst to produce hydrogen iodide

H2 + l2 ➜ 2Hl

Question: 855

Why sodium metal is more reactive than magnesium ?

Answer: 855

855-861

Magnesium is harder then sodium because density of sodium is 0.98cm ^-3and density of magnesium is 1.74gcm³ . Sodium is too soft to be cut with knife

Question: 856

Give the non-metallic trend in halogens .

Answer: 856

856-861

Elements of group of periodic table consists of fluorine ,chlorine, bromine , iodine . and astatine

Their non-metallic nature decrease down the group . Fuorine is most metallic ,while iodine is least non-metallic

Question: 857

Name the metal which is least conductor of heat ?

Answer: 857

857-861

Lead is a metal which is least conductor of heat

Question: 858

What is relation between electropositivity and ionization energy ?

Answer: 858

858-861

Electropositivity is the reverse of the ionization energy . In the from from top to bottom ionization energy decreases and electropositivity increases

Question: 859

Give the reaction of mangnesium with O2 And N2 .

Answer: 859

859-861

Reaction of magnesium with O2 :