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12th Class Chapter 7 Chemistry Short Questions

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Question: 1
Write a short note on cracking of petroleum?
Answer: 1
1-41
Breaking of higher hydrocarbons having high boiling point into a variety of lower hydrocarbons which are more volatile (low boiling) is called cracking of petroleum.
Question: 2
Write down the important used of organic compounds in our daily life?
Answer: 2
2-41
  1. Organic Compounds are used to synthesize proteins ,enzymes carbohydrates ,lipids vitamins and nucleic acid by living bodies.
  2. These compounds are used to produce medicine,.clothing,chemical food etc.
Question: 3
Define Refiner?Mention oil refineries in Pakistan?
Answer: 3
3-41
Crude oil is when extracted from rocks it appear like a liquid of blackish colour,It is refined to got different petroleum fraction.At present four oil refineries are in operation in our country.One oil refinery knowns as Attock Oil refinery is located at two oil refineries have been established at karachi which have about 2.13 million tons of oil refining capacity.Another refinery as Pak-Arab refinery is located at Mahmud kot.
Question: 4
How is coal produced from the remains trees?
Answer: 4
4-41
Coal in nature was formed from the remains of the trees buried inside the earth crust some 500 million years ago,Due to the bacterial and chemical pressure inside the earth crust,peat got transferred into crust this process is called carbonization of coal,Coal is important solid fuel and becomes a source of organic compound.
Natural Gas: It is an important mean of energy especially for countries like Pakistan which are deficient in the production of mineral oil and coal.It is mixture of low boiling hydrocarbons.
Petroleum:Mineral oil is called petroleum when it is in the refined from it is thought to have been formed by slow chemical and biochemical decomposition of the remains of the organic matter found between the sedimentary rocks.
Question: 5
Branched hydrocarbons are better as a fuel as compared to straight chain?
Answer: 5
5-41
Straight chain hydrocarbons have low octane numbers and make poor fuels.
Question: 6
What is Vital force of theory?
Answer: 6
6-41
Early scientist believe that the organic compound could be manufactured only by and within living thing and these compounds could be synthesized from inorganic material this theory was referred to as Vital force theory.
Question: 7
Why vital force of theory is rejected?
Answer: 7
7-41
Vital force of theory was rejected by Friedrich Wohler when he synthesized urea an organic compound from ammonium cyanate a substance ok known mineral origin.
Since the synthesis of urea from ammonium cyanate ,million of organic compounds have been prepared and analyzed.
Question: 8
What is meant by Carbonization?
Answer: 8
8-41
Coal in nature was formed from the remains of the trees buried inside the earth crust some 500 million ago.Due to the bacterial and chemical pressure inside the earth crust ,peat got transformed into coal,This process is called Carbonization of coal.
Question: 9
Write down any two characteristics feature of organic compound?
Answer: 9
9-41
Non Ionic Character of Organic Compound:Organic Compounds are generally covalent compound ,therefore do not give ionic reaction.
Isomerism:Isomerism is a very common phenomena in organic compounds.very often more than one compound are represented by the same molecule formula.However they have different structural formulas.
Question: 10
Describe the natural source of methane in atmosphere.
Answer: 10
10-41
Methane Is and important mean of energy especially for countries like in Pakistan which are deficient in the production of mineral oil and coal.It is a mixture of low boiling hydrocarbons,Major portion of the natural gas is methane.It is so formed by the decomposition of organic matter,
Question: 11
Name organic compound first of all prepared in the laboratory and how?
Answer: 11
11-41
Friedrick Wohler synthesized urea,an organic compound from ammonium cyanate ,a substance of known mineral origin.
NH4CNO ---------- (NH2)2CO
Question: 12
What is the significance of Wohler work?
Answer: 12
12-41
Friedrick Wohler synthesized urea (NH2)2CO,an organic compound from ammonium cyanate a substance of known mineral organic.Since the synthesis of urea from ammonium cyanate ,million of organic compound have been prepared and analyzed.
Question: 13
Give names of four compounds which are homocyclic but are not aromatic?
Answer: 13
13-41
1.cyclopropane 2.cyclobutane 3.cyclo penatane 4. cyclohexane
Question: 14
Octane number of gasoline is improved by reforming.
Answer: 14
14-41
The octane number of gasoline is improved by a process called reforming.It involves the conversion of straight hydrocarbons into branched chain b heating in the absence of oxygen and in the presence of catalyst.
Question: 15
Differentiate between alicyclic and aromatic compounds?
Answer: 15
15-41
Alicyclic Compounds:Thehomocyclic compounds which contain a ring of three or more carbons atom and resembling aliphatic compounds are alicyclic compounds ,The saturated alicyclic hydrocarbons have the general formula C2H2n.
Question: 16
Differentiate between homocyclic and heterocyclic compounds?
Answer: 16
16-41
The compounds in which the ring consists of only carbon atom,These are called carbocyclic compounds,Homocyclic Alicyclic compound are further classified as
  1. Alicyclic compound
  2. Aromatic compound
Heterocyclic compound: The compound in which the ring consists of atom of more than one kind are called heterocyclic compound,In heterocyclic compound generally one or more atom of element such as nitrogen,oxygen or sulphur are present.
Question: 17
Define open chain compound.
Answer: 17
17-41
Open chain may be branched or non branched .Open chain hydrocarbons are also called aliphatic compounds.
Branched chain compounds: Those organic compounds in which the carbon atom are attached on the side of the chain.
Question: 18
Define Thermal cracking.
Answer: 18
18-41
Breaking down of large molecule by heating at high temperature and pressure is called thermal cracking.It is particularly useful in the production of unsaturated hydrocarbons such as ethane and propene.
Question: 19
What is catalytic cracking?
Answer: 19
19-41
Higher hydrocarbons can be cracked at low temperature and lower pressure ,in the presence of suitable catalyst .A typical catalyst.A typical catalyst used for this purpose is a mixture of silica and alumina ,Catalytic cracking produces gasolines of higher octane number and therefore this method is used for obtaining better quality gasoline.
Question: 20
Give idea about knocking in the internal combustion engine.
Answer: 20
20-41
The gasoline fraction present in petroleum in generally not of good quality.When it burn in an automobile engine ,combustion can be initiated before the spark plug fire ,This produced a sharp metallic sound called knocking which greatly reduced the efficiency of an engine.
Question: 21
Write importance of cracking.
Answer: 21
21-41
Besides increasing the yield of gasolines,cracking has also produced large amount of useful by products,such as 60 ethane,propane,butane and benzene.These are used for manufacturing drugs,plastic ,detergents ,synthetic fibres,fertilizers weed killer and important chemical like ethanol,phenol and acetone.
Question: 22
What are carbocyclic compound?
Answer: 22
22-41
The compound in which the ring consists only carbon atom is called the carbocyclic compound.
Question: 23
Define reforming of petroleum and give one example?
Answer: 23
23-41
The octane number of gasoline is improved by a process is called reforming,It involved the conversion of straight chain hydrocarbons into branched chain by heating in the absence of oxygen and in the presence of catalyst.
Question: 24
Why there is a free rotation around in a single bond ,but no free rotation around a double bond?
Answer: 24
24-41
Two carbons atom joined by a single bond are capable of free rotation about it,However when two carbons atom are joined by a double bond ,they can not rotate freely.As a result the relative positions of the various groups attached to these carbon atoms get fixed and give rise to cic-trans isomers.
Question: 25
Define Catenation?
Answer: 25
25-41
  1. The property of carbons atoms to link with other carbons atom to form long chain or rings is called catenation,The main reasons of such large number of compounds is catenation of carbons atoms
Question: 26
Write a brief note on geometric isomerism?
Answer: 26
26-41
Such components which possess the same structural formula,but differ with respect to the position of the identical groups in space are called geometric isomers,and the phenomena is known as the geometric isomers.Two carbons atom joined by a single bond are capable of free rotation about it,However when two carbons atom are joined by a double bond,they cannot rotate freely.As a result the relative and give rise to cis-trans isomers.
Question: 27
Why is restricted rotation necessary to show the geometrical isomerism?
Answer: 27
27-41
Two carbons atom joined by a single bond are capable of free rotation about it.However when two carbon atom are joined are joined by a double bond they can not rotate freely,As a result the relative position of the various groups attached to these carbons atoms get fixed and give rise to cis-temperature.
Question: 28
What id Atomic Hybridization?
Answer: 28
28-41
Mixing up of atomic orbitals to form new;y generated orbitals of same energy and same shape is called atomic orbital hybridization.For example : in carbon electron from the 2s orbital is promoted to an empty 2p2orbital giving electron configuration.
Question: 29
What are fused rings aromatic compounds?
Answer: 29
29-41
The aromatic compounds in which two or more than two benzene rings are fused together are called fused aromatic compounds.
Question: 30
Define tautumerism.
Answer: 30
30-41
This type of isomerism arises due to shifting of proton from one atom to other in the same molecule.
Question: 31
In alkanes sp3hybridization occurs.Discuss?
Answer: 31
31-41
In the formation of alkane ,the four hybrid atomic orbital of carbon overlap separately with four atomic orbitals to form four equivalent bonds.For example in ethane two tetrahedrons of each carbons are joined together.
Question: 32
When does sp3- Hybridization occur?
Answer: 32
32-41
When one s and three p orbitals mix together to form four new equivalent hybrid atomic orbitals having same shaper and energy.This mode of hybridization is called tetrahedral hybridization .All these four sp3 hybrid orbitals are degenerated and are directed at an angle of 109.5 in space to give a tetrahedral geometry.
Question: 33
What does sp-hybridization occur?
Answer: 33
33-41
When one 2s one 2p orbitals of the carbon atom mix together to give rise to two degenerated sp hybridized atomic orbitals.These orbitals have linear shape with a bond angle of 180 Degree.
Question: 34
1-Butyne does not show geometrical isomerism but 2-Butene does .Give reasons?
Answer: 34
34-41
The necessary and sufficient conditions for a compound to exhinit geomatric isomersim is that the two groups attached to the same carbon must be different,
In 1-Butene similar hydrogen atom are attached to the same carbon atom ,so it does not exhibit geometric isomerism.
But 2-Butene can exist in the form of cls and trans isomers.
Question: 35
Draw the structure of C2H2and indicate the bond angles?
Answer: 35
35-41
Ethyne molecule is formed when two sp hybridized carbons atom join together to form alpha bond by sp-sp overlap.The other sp-orbitals is utilized to form a alpha bond with 1s orbitals of hydrogen atom.
Question: 36
Define position isomerism.
Answer: 36
36-41
The isomerism arises due to the difference in the position of the same functional group on the carbon chain,the arrangement of carbon atom remains the same.
Question: 37
Define function group.Give two example of functional group containing oxygen?
Answer: 37
37-41
An atom or a group of atom or a double bond or triple bond whose presence imparts specific properties to organic compounds is called a function; group,because they are chemically functional parts of molecule.
Question: 38
Cis-trans isomerism is a result of restricted rotation of carbon-carbon double bond.Discuss?
Answer: 38
38-41
Two carbon atom joined by a single bond are capable of free rotation about it .However when two carbons atom are joined by a double bond,they can not rotate freely ,As a result the relative positions of the various groups attached to these carbons atoms get fixed and give rise to cis trance isomers.
Question: 39
Define functional group isomerism .
Answer: 39
39-41
An atom or group of atoms or a double bond or a triple bond whose presence imparts specific properties to organic compounds is called a functional group because they are chemically functional part of molecules.
Question: 40
What are the conditions for cis and Trans isomerism?
Answer: 40
40-41
The necessary and sufficient condition for a compound to exhibit geometric isomerism is that the two groups attached to the same carbon must be different.
Question: 41
What is metamerism?
Answer: 41
41-41
Isomerism arises due to the unequal distribution of carbon atom on either side of the functional group ,Such compound belong to the same homologous series.

12th Class Chemistry Chapters Short Questions