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12th Class Chapter 5 Chemistry Short Questions

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Question: 1
Why the lattice energy of Fluorides is greater than Chlorides?
Answer: 1
1-38
Due to small size of fluoride ions(f),there will be a better overlap of orbitals and consequently leads to shorter and stronger bonds with other elements.Ionic fluorides have higher lattice energies than the chlorides and the value is responsible for the insolubility of the fluorides in water.Due to low dissociation energy of fluorine molecule,it is highly reactive.The other halogens react slowly under similar conditions.The fluorides are,however more stable with respect to dissociation into elements.
Question: 2
Why iodine has metallic luster?
Answer: 2
2-38
Due to big size of lodine outer electrons are excited by taking light and due to excitation and de-excitation gives metallic luster.
Question: 3
On what factor oxidizing power of halogens depends upon?
Answer: 3
3-38
  1. Energy of dissociation
  2. Electrons affinity of atoms
  3. Heat of vapourization
Question: 4
Give reason that fluorine is gas ,iodine is solid?
Answer: 4
4-38
Iodine molecule has larger size than fluorine,The intermolecular attraction is greater in the larger molecule having greater masses.Due to the larger size of iodine molecule the van der Waal forces are stronger than smaller size molecule of fluorine.
Question: 5
Compare halogen acids in their reducing properties?
Answer: 5
5-38
HF,HCI,HBr and HI acts as reducing agents in the following order:
HF<HCI < HBr<HI
Question: 6
Why Fluorine acts as a strong oxidation agent?
Answer: 6
6-38
Oxidizing power of fluorine is higher,because it has low energy of dissociation and higher hydration energy of its ions,Due to the relative strength as oxidizing agents,it is possible for each free halogen to oxidize the ions of other halogens next to it in the family .Fluorine can oxidize all the halide ions molecule halogens.
Question: 7
The elements of group VIII-A are called noble gases.Comment?
Answer: 7
7-38
Elements of group VIII-A are called noble gases because,these elements are colourless,odourless monoatomic gases which are chemically un-reactive.
Question: 8
Why oxidizing power of F2is higher than other halogens?
Answer: 8
8-38
Oxidizing power of F2is higher ,because it has low energy of dissociation and higher hydration energy of its ions,Due to the relative strength as oxidizing agents it is possible for each free halogens to oxidize the ions of other halogens next to it in the family.
Question: 9
Arrange the following ions in order of increasing size F,CI,Br,I
Answer: 9
9-38
F<CI<Br<I
Question: 10
Halogens are strong oxidizing agents ,Justify.
Answer: 10
10-38
All the free halogens acts as oxidizing agents when they reacts with metals or nonmetals.On forming ionic compounds with metals,the halogen s gain electron and are converted to negative halide ions.
Question: 11
What is peculiar behaviour of Fluorine?
Answer: 11
11-38
The halogen form a homologous series but fluorine differ from the other halogens in many respects which is due to :
  1. Small in size of D atom and F ion,
  2. High first ionization energy and electronegativity.
  3. Low dissociation energy of F2molecule as compared to CI2and Br2.
  4. Restriction of the valence shell to an octet
  5. Direst combination with inert gasses.
Question: 12
Why oxidizing power of halogens decreases down the group?
Answer: 12
12-38
Oxidizing power of halogens depends upon the following factors:
  1. Energy of dissociation
  2. Electron affinity of atoms
  3. Hydration energy if ions
  4. Heat of vapourization
While going down the group all above mentioned factors decreases, All the free halogens acts as oxidizing agents when they reacts with metals or non metals,On forming ionic compound with metals ,the hydrogens as gain of electrons and are converted to negative halide ions.
Question: 13
Write four properties of hydrogen fluorides?
Answer: 13
13-38
  1. HF is a colourless volatile liquid.
  2. HF attacks glass and has found application as non aqueous solvent.
  3. HF has meeting point as -83.8 degree,
  4. HF has boiling point as 19.5 degree.
Question: 14
Give one method of preparation and one use of I2O5?
Answer: 14
14-38
Preparation : It can be prepared by heating iodic acid at 240oDegree,
it is used for the quantitative analysis of CO.
Question: 15
Perchloric acid is considered as valuable analytical reagent.Why?
Answer: 15
15-38
Due to oxidizing effect of perchloric acid it is considered as valuable analytical reagent.
Question: 16
Define "disproportion reaction".
Answer: 16
16-38
A reaction in which a species(molecule atom or ion )is simultaneously oxidized and reduced is called disproportion reaction.
Question: 17
Arrange the following oxyacids in increasing order of acid strength and oxidizing power ; HCIO4>HCIO2>HCIO
Answer: 17
17-38
HCIO4>HCIO2>HCIO
Question: 18
HXO4is strongest oxyacid .Explain.
Answer: 18
18-38
The acidic strength increase with the increase in the number of oxygen atoms ,As the oxidation state of the halogen increase the bonding electrons are shifted away from the H-atom and the tendency of the molecule to loss a proton increase,This accounts for the change of strength of oxyacids,HXO4has four oxygen atom,so it is strongest oxyacid.
Question: 19
HF is a weak acid while HCI is strong acid.Give reason.
Answer: 19
19-38
The strength hydrogen halogen bond is very high in HF,The bond strength is reflected in the case of dissociation of hydrogen and halides,Hydrofluoric acid is a week acid due to limited ionization than hydrochloric acid.
Question: 20
How bleaching powder is prepared by Hasenclever method?
Answer: 20
20-38
The apparatus used in this method consists of 4 to 8 iron cylinders placed one above the other horizontal ,They are interconnected and provided with stirrers,The slaked lime is added in through a hopper in the upper cylinder and transported from one cylinder rises p and reacts with slacked lime form bleaching powder ,which is collected through the outlet in the lower cylinder.
Question: 21
Why HF is weaker acid that other halogen acid?
Answer: 21
21-38
In water hydrogen halides give hydrofluoric ,hydrochloric ,hydrobromic and hydroiodic acid,The strength hydrogen halogen bond is very high in HF.The bond strength is reflected in the case of dissociation of hydrogen and halides,Hydrofluoric acid is week acid due to limited ionization,The other three acid are very strong acids,The acidic strength increase in order.
Question: 22
Describe factor of acidic strength of oxyacids of halogens?
Answer: 22
22-38
  1. Number of oxygen atoms attached to the oxyacid halogens.
  2. oxidation state of hydrogen in oxyacid of halogens.
  3. Tendency to lose proton from oxyacid of halogens.
Question: 23
How halogen acids are ionized in water?
Answer: 23
23-38
In water hydrogen halides give hydroflorine ,hydrochloric,hydrobromic and hydrochloric acids.Hydrofluoric acid is week acid due to limited ionization,The other three acids are vert strong acid,The acidic strength increases in the order.
Question: 24
Write two use of bleaching powder?
Answer: 24
24-38
Bleaching powder is used :
  1. for the laboratory preparation of chlorine and oxygen.
  2. for making unshrinkable wool.
Question: 25
Write two uses of halogen?
Answer: 25
25-38
  1. Fluorine is used for the preparation of freons,which is being used in refrigerator and aerosol propellants.
  2. Chlorine is used in the manufacturing of bleaching powder.
Question: 26
What are ferons and Teflons?
Answer: 26
26-38
Ferons: Fluorine is used for the preparation of freons,Freons is the commercial name of low molecular mass fluoro chloro carbons.These are being used as the refrigerants and aerosol propellants.
Teflons:Fluorine is used for the preparation of Teflon,It is polymerized tetrafluoroethylene compound.It is valuable plastic which resists the action of oxidants,acid and alkalies.
Question: 27
Write two application of noble gases?
Answer: 27
27-38
1.Helium is used in weather balloons,in welding and in traffic signal light.
2.Helium is used as a cooling medium for nuclear laser.
3.Argon is used for arc welding and cutting.
Question: 28
What is Halothane ?Write its formula.
Answer: 28
28-38
Definition: Chemical compounds of halogens with ethylene is called halothane.
Formula: Fluorine is used to firm Teflon(-CF2-CF2-)n.
Question: 29
What is iodize salt?
Answer: 29
29-38
When sodium or potassium iodine is added to the common salt,then the common salt is called iodized salt.
Question: 30
What are the commercial use of halogens and their compounds?
Answer: 30
30-38
  1. Fluorine is used for the preparation of ferons,Which is being used in refrigerants and aerosol propellants.
  2. Fluorine is used to prepare Teflon.
  3. Iodine is used in pharmaceutical industries as disinfectants and germicides.
Question: 31
What is meant by available chlorine?
Answer: 31
31-38
If excess of an acid is added to bleaching powder ,chlorine is given out.
The amount of chlorine thus set free is called available chlorine,The activity of bleaching powder is measured in terms of available chlorine,The average percentage of available chlorine in bleaching powder is 35-40%.
Question: 32
What are the major application of Neon?
Answer: 32
32-38
Neon is largely is used in making neon advertising signs,in high voltage indicators and TV tubes,Neon and helium arc is used in making glass laser.
Question: 33
What is bleaching powder?
Answer: 33
33-38
Bleaching powder is yellowish white powder with strong smell of chlorine and is used to bleach different things.It has chlorine known as "available chlorine".
Question: 34
What are noble gasses?Why are they inert?
Answer: 34
34-38
Elements of group VIII-A are called noble gases because these elements are colourless odourless monatomic gases which are chemically unreactive.
Noble gases are inert due to the completion of their outermost shell. These gases have complete electronic configuration and have filled duplet and octet.
Question: 35
Give uses of iodine.
Answer: 35
35-38
The major application of iodine are in pharmaceutical industry,It is used as disinfectants and germicides,Tincture of iodine and iodex are popular preparation of iodine.Diet with insufficient iodine ions leads to an enlargement of the thyroid,To ensure the present of iodine ion in the diet,sodium or potassium iodine is added to the common salt which is known as iodized salt.
Question: 36
Write any two use of Krypton?
Answer: 36
36-38
Krypton is used to fill fluorescent tubes and in flash lamps for high speed photography.
Question: 37
Give two used of bromine?
Answer: 37
37-38
Ethylene dibromide added to gasoline to save the engine from lead oxide and leaf sulphate deposits.Bromide is also used as fungicide,Silver bromide is used in photography.
Question: 38
Give two application of Radon gas.
Answer: 38
38-38
1.Radon is being radioactive is used in earthquake prediction.
2.Radon being radioactive is used in radiotherapy for cancer.

12th Class Chemistry Chapters Short Questions