Chapter 12 : Organic Chemistry - Selina Solutions for Class 10 Chemistry ICSE

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Chapter 12 - Organic Chemistry Excercise Intext 1

Question 1

Give the name of one member of each of the following:

(a) Saturated hydrocarbons

(b) Unsaturated hydrocarbons


Solution 1

The member of each of the following is:

(a) Saturated Hydrocarbon: Hexane (C6H14)

(b) Unsaturated Hydrocarbon: Hexene (C6H12)

Question 2

(a) What are organic compounds?

(b) What is the Vital force theory? Why was it discarded?

Solution 2

(a) Organic chemistry may be defined as the chemistry of hydrocarbons and its derivatives.

(b) Vital Force Theory is a theory made by the Scientist Berzelius in 1809 which assumed that organic compounds are only formed in living cells and it is impossible to prepare them in laboratories.

It was discarded because Friedrich Wohler showed that it was possible to obtain an organic compound(urea) in the laboratory.

Question 3

(a) Name a few sources of organic compounds

(b) Give the various applications of organic chemistry

Solution 3

(a) Few sources of organic compounds are:

Plants

Animals

Coal

Petroleum

Wood

(b) The various applications of organic chemistry is:

It is used in the production of soaps, shampoos, powders and perfumes.

Various fuels like natural gas, petroleum are also organic compounds.

The fabrics that we use to make various dresses are also made from organic compounds.

Question 4

Organic chemistry plays a key role in all walks of life. Discuss

Solution 4

Organic compounds are present everywhere. They are present in:

It is present in the production of soaps, shampoos, powders and perfumes.

It is present in the food we eat like carbohydrates, proteins, fats, vitamins etc.

Fuel like natural gas, petroleum are also organic compounds.

Medicines, explosives, dyes, insecticides are all organic compounds.

Thus we can say that organic compounds play a key role in all walks of life.

Question 5

Carbon shows some unique properties, name them.

Solution 5

The unique properties shown by carbon are:

Tetravalency of carbon

Catenation

Isomerism

Question 6

Explain the following:

(a) Tetravalency

(b) Catenation

Solution 6

(a) Tetravalency: Carbon can neither lose nor gain electrons to attain octet. Thus it shares four electrons with other atoms. This characteristics of carbon by virtue of which it forms four covalent bonds, is called Tetravalency of carbon.

In structural form :

(b) Catenation: The property of self -linking of atoms of an element through covalent bonds in order to form straight chains, branched chains and cyclic chains of different sizes is known as catenation.

Carbon- carbon bond is strong so carbon can combine with other carbon atoms to form chains or rings and can involve single, double and triple bonds.

Question 7

Write any four properties of organic compounds that distinguish them from inorganic compounds.

Solution 7

Four properties of organic compound that distinguish them from inorganic compounds are:

(i) Presence of carbon.

(ii) Solubility in the organic solvents.

(iii) Forming of covalent bonds.

(iv) Having low melting and boiling points.

Question 8

Why are organic compounds studied as a separate branch of chemistry?

Solution 8

Due to the unique nature of carbon atom, it gives rise to formation of large number of compounds. Thus this demands a separate branch of chemistry.

Question 9

What are Hydrocarbons? Compare saturated and unsaturated hydrocarbons?

Solution 9

Hydrocarbons are compounds that are made up of only carbon and hydrogen.

Comparison of saturated and Unsaturated hydrocarbons:

Saturated Hydrocarbon

Unsaturated Hydrocarbon

1. Carbon atoms are joined only by single bonds.

Carbon atoms are joined by double or by triple bonds.

2. They are less reactive due to the non-availability of electrons in the single covalent bond.

They are more reactive due to presence of electrons in the double or the triple bond.

3. They undergo substitution reaction.

They undergo addition reaction.

Question 10

Give reason for the existence of large numbers of organic compounds

Solution 10

Due to presence of unique properties of carbon like Tetravalency, catenation and Isomerism large number of organic compounds are formed.

Question 11

Give at least one example in each case to show structure of isomers of

(a) Single bond compound

(b) Double bond compound

(c) Triple bond Compound

Solution 11

(a) Single Bond compound: For example: In pentane

 

(b) Double bond compound: For example:- In pentene

 

(c) Triple bond compound: In case of Hexyne:

 

Question 12

Name a compound of each type and draw the figure.

(a) Cyclic compound with single bond

(b) Cyclic compound with triple bond

Solution 12

(a) Cyclic compound with single bond: cyclopentane

Structure:

(b) Cyclic compound with triple bond: cyclopentyne

Structure:

Question 13

Define substitution and addition reaction.Give an example for each.

Solution 13

Substitution reaction: A reaction in which one atom of a molecule is replaced by another atom (or group of atoms) is called a substitution reaction.

Addition reaction: A reaction involving addition of atom(s) or molecules(s) to the double or the triple bond of an unsaturated compound so as to yield a saturated product is known as addition reaction.

Question 14

Define or explain chain isomerism and position isomerism with examples in each case.

Solution 14

Chain isomerism

Chain isomerism arises due to the difference in arrangement of C atoms in the chain. For example, there are two isomers of butane, C4H10. In one of them, the carbon atoms lie in a "straight chain" whereas in the other the chain is branched.

Position isomerism

It is due to the difference in position of functional groups.

For example, there are two structural isomers with the molecular formula C3H7Br. In one of them, the bromine atom is on the end of the chain, whereas in the other it is attached in the middle.

Question 15

(a)Define the term isomerism. State two main causes of isomerism?

(b) (b) Draw the chain isomers of hexane (C6H12).

(c) Draw position isomers of butene (C4H8)

Solution 15

(a)Isomerism: Compounds having the same molecular formula but different structural formula are known as isomers and the phenomenon as isomerism.

Two main causes of isomerism are:

Difference in mode of linking of atoms.

Difference in the arrangement of atoms or groups in space.

(b) 

(c)  

CH2=CHCH2CH3               H3C-CH=CHCH3

1-butene                              2-butene

Question 16

Define a functional group and give the structural formula of the following functional group:

(a) Ketons

(b) Alcohols

(c) Aldehydes

Solution 16

A functional group is an atom or a group of atoms that defines the structure (or the properties of a particular family) of organic compounds.

 

The structural formula of

(a) Halides :-R-X

Example:

(b)Alcohols:- R-OH

Example:

(c) Aldehydes:-R-CH=O

Example:

Question 17

Write the name and formula of the fourth member of the following homologous series:

a. Alkyne

b. Alcohol

Solution 17

a. Butyne; its formula is C4H6.

b. Butanol; its formula is C4H9OH.

Question 18

Which part of an organic compound determines

(i) Physical properties

(ii) Chemical properties

Solution 18

(i) Physical properties: The alkyl group determines the physical properties.

(ii) Chemical properties: The functional group is responsible for the chemical properties.

Question 19

Name the alkyl radical and the functional group of the following organic compounds:

(a) CH3OH

(b) C2H5OH

(c) C3H7CHO

(d) C4H9COOH

(e) CH3COOH

(f) HCHO


Solution 19

The alkyl radical and the functional group are:


Sr.No

Formula

Name of alkyl radical

Name of Functional group

a

CH3OH

Methyl

Alcohol

b

C2H5OH

Ethyl

Alcohol

c

C3H7CHO

Propyl

Aldehyde

d

C4H9COOH

Butyl

Carboxyl

e

CH3COOH

CH3

COOH

f

HCHO

H

CHO

Question 20

(a) What is an alkyl group?

(b) Give the names of any three alkyl radicals. How are they formed?

Solution 20

 

(a) An alkyl group is obtained by removing one atom of hydrogen from an alkane molecule. Alkyl group is named by replacing the suffix 'ane' of the alkane with the suffix -yl.

(b) The name of three alkyl radicals are:

Methyl

Ethyl

Propyl

 

They are formed by removing 1 hydrogen from an alkane.

CH4-CH3+H+

Methyl

CH3-CH3 CH3-CH2 -+ H+

Ethyl

CH3-CH2-CH3 CH3-CH2-CH2 -+ H+

Propyl

Question 21

Give the names and the structural formula of the first three members of the homologous series of alkanes

Solution 21

The names and the structural formula of first three members of the homologous series of alkane are:

(i)

CH4Methane

(ii)

C2H6Ethane

(iii)

C3H8Propane

Question 22

(a) What is a Homologous series?

(b) What is the difference in the molecular formula of any two adjacent homologues:

(i) In terms of molecular mass

(ii) In terms of number and kind of atoms per molecule?

Solution 22

(a) A homologous series is a group of organic compounds having a similar structure and similar chemical properties in which the successive compounds differ by a CH2 group.

(b) The difference in molecular formula of any two adjacent homologues is

(i) It differs by 14 a.m.u in terms of molecular mass.

(ii) It differs by three atoms. The kind of atoms it differs is one carbon and two hydrogen.

Chapter 12 - Organic Chemistry Excercise Ex. 12A

Question 1

Solution 1

Methanal

Question 2

  

Solution 2

Propanol

Question 3

Write the IUPAC name of the following:

  

Solution 3

2,2 dimethyl propane

Question 4

Write the IUPAC name of the following:

  

Solution 4

2-methyl butane

Question 5

Write the IUPAC name of the following:

  

Solution 5

Propene

Question 6

Write the IUPAC name of the following:

  

Solution 6

2,2-dimethyl pentane

Question 7

Write the IUPAC name of the following:

CH3 - C = C - CH2CH2

Solution 7

Pent-2-ene

Question 8

Write the IUPAC name of the following:

  

Solution 8

3-methyl but-1-yne

Question 9

Write the IUPAC name of the following:

  

Solution 9

2,3-dimethyl pentane

Question 10

Write the IUPAC name of the following:

  

Solution 10

3-methyl heptane

Question 11

Write the IUPAC name of the following:

Solution 11

2-Butene

Question 12

Write the IUPAC name of the following:

Solution 12

Hept-2-yne

Question 13

Write the IUPAC name of the following:

  

Solution 13

5,5-dimethyl hexan-1-al

Question 14

Write the IUPAC name of the following:

  

Solution 14

Pentan-2-ol

Question 15

Write the IUPAC name of the following:

  

Solution 15

4-methyl pentan-1-oic acid

Question 16

Write the IUPAC name of the following:

  

Solution 16

2-bromo-2-methyl butane

Question 17

Write the IUPAC name of the following:

  

Solution 17

1-bromo-3-methyl butane

Question 18

Write the IUPAC name of the following:

  

Solution 18

Prop-1-yne

Question 19

Write the IUPAC name of the following:

  

Solution 19

Ethanoic acid

Question 20

Write the IUPAC name of the following:

Solution 20

1,2-dichloroethane

Question 21

Write the structures of the following compounds:

(a) Prop-1-ene

(b) 2,3-dimethylbutane

(c) 2-methylpropane

(d) 3-hexene

(e) Prop-1-yne

(f) 2-methylprop-1-ene

(g) Alcohol with molecular formula C4H10O

Solution 21

The structure of the following compounds are:

(a) Prop-1-ene

CH3-CH=CH2

(b) 2,3-dimethylbutane

CH3-CH(CH3)-CH(CH3)-CH3

(c) 2-methylpropane

CH3-CH(CH3)-CH3

(d) 3-hexene

CH3-CH2-CH=CH-CH2-CH3

(e) Prop-1-yne

CH3-C?CH

(f) 2-methylprop-1-ene

CH3-C(CH3)=CH2

(g) Alcohol with molecular formula C4H10O

CH3-CH2-CH2-CH2-OH

Question 22

Choose the correct answer:

(a) C5H11 is an

(i) Alkane (ii) Alkene (iii) Alkyne (iv) Alkyl group

 

(b) A hydrocarbon of the general CnH2n is

(i) C15H30 (ii) C12H26 (iii) C8H20 (iv) C6H14

 

(c) A hydrocarbon with molecular mass 72 is

(i) An alkane(ii) an alkene (iii) an alkyne

 

(d) The total number of different carbon chains that four carbon atoms form in alkane is

(i) 5 (ii) 4 (iii) 3 (iv) 2

 

(e) CH3-CH2-OH and CH3-O-CH3 are

(i) Position isomers (ii) chain isomers (iii) homologous (iv) functional group isomers

 

(f) The IUPAC name of the compound is

(i) 3-trimethylhexane (ii) 3-methyl hexane (iii) 4-methyl hexane

Solution 22

(a) Correct answer: (iv)

CnH2n+1 is the formula for alkyl group. Hence it is C5H11.

 

(b) Correct answer: (i)

A hydrocarbon of general CnH2n is C15H30.

 

(c) Correct answer: (ii)

As the formula of Alkene is CnH2n. Thus n+2n=72

3n=72

n=24

By filling value we get the molecular mass 72.

 

(d) (iv)

The total number of carbon chains that four carbon atoms form in alkane is 2.They are:

 

 

(e) Correct answer: (iv)

Alcohol and ether are functional isomers as they have same molecular formula but different functional groups.

 

(f) Correct answer: (ii)

The IUPAC name of this compound is: 3-methyl hexane.

Question 23

Fill in the blanks using the appropriate words given in the brackets :

(a) Propane and ethane are________. (Homologues, isomers)

(b) A saturated hydrocarbon does not participate in a/an _________ reaction.(substitution, addition)

(c) Succeeding members of a homologous series differ by______. (CH,CH2,CH3)

(d) As the molecular masses of hydrocarbons increase, their boiling points ______ and melting point ______. (increase, decrease)

(e) C25H52 and C50H102 belong to ______ homologous series.(the same, different)

(f) CO is an _______Compound.(organic, inorganic)

(g) The chemical properties of an organic compound are largely decided by the ........ and the physical properties of an organic compound are largely decided by the _______. (functional group, number of carbon atoms)

(h) CHO is the functional group of an______. (alcohol, aldehyde)

(i) The root in the IUPAC name of an organic compound depends upon the number of carbon atoms in______. (any chain, principal chain)

(j) But-1-ene and but-2-ene are examples of _____ isomerism. (Chain , position , functional)

Solution 23

(a) Propane and ethane are homologues.

(b) A saturated hydrocarbon does not participate in a/an addition reaction.

(c) Succeeding members of a homologous series differ by CH2.

(d) As the molecular masses of hydrocarbons increase, their boiling points Increase and melting point increase.

(e) C25H52 and C50H102 belong to the same homologous series.

(f) CO is an organic Compound.

(g) The chemical properties of an organic compound are largely decided by the functional group and the physical properties of an organic compound are largely decided by the number of carbon atoms. 

(h) CHO is the functional group of an aldehyde.

(i) The root in the IUPAC name of an organic compound depends upon the number of carbon atoms in Principal Chain.

(j) But-1-ene and but-2-ene are examples of position isomerism.

Question 24

Draw the structural formula for each of the following compounds:

a. isomer of n-butane

b. vinegar

c. 2-propanol

d. ethanol

e. acetone

f. diethyl ether

What is used to describe these compounds taken together?

Solution 24

a. 

 

b. 

 

 

c. 

 

 

d. 

 

 

e. 

 

 

f. 

Question 25

a. What is the special feature of the structure of 

 i. C2H4

 ii. C2H2  

b. What type of reaction is common to both these compounds? Why does methane not undergo this type of reaction?

(c) What is IUPAC name of dimethyl ether.

Solution 25

a. 

i.  (Ethene)

 In the above structure, both carbons are bonded

 with double bonds.

ii.   (Ethyne)

 In the above structure, both carbons are bonded

 with triple bonds.

b. Addition reactions are common to both these compounds. Methane does not undergo this type of reaction because it is bounded with four hydrogen atoms, while in ethane, double bonds break and provide a site for addition.

(c) Methoxymethane

Question 26

Which type of reaction will (i) ethane and (II) ethane undergo?

Solution 26

(i) Ethane undergoes substitution reactions.

(ii) Ethene undergoes addition reactions.

Question 27

Choosing only words from the following list, write down appropriate words to fill in the blanks from (a) to (e) given below. Addition, carbohydrates, CnH2n-2, CnH2n,CnH2n+2, electrochemical homologous, hydrocarbon, saturated, substitution, unsaturated.

The alkanes form an (a) ………… series with the general formula (b) ………….. The alkanes are (c) …………. (d) …………… which generally undergo (e) …………. reactions.

Solution 27

The alkanes form an (a) electrochemical homologous series with the general formula (b) CnH2n+2. The alkanes are (c) saturated (d) hydrocarbons which generally undergo (e) substitution reactions.

Question 28

Draw the structural formula of a compound with two carbon atoms in each of the following cases.

a. An alkane with a carbon to carbon single bond

b. An alcohol containing two carbon atoms

c. An unsaturated hydrocarbon with a carbon to carbon  triple bond

Solution 28

 a.

 

 

 b.

 

 c.

 

Question 29

Ethane, Ethene, Ethanoic acid, Ethyne, Ethanol From the above, name

a. The compound with -OH as the part of its structure.

b. The compound with -COOH as the part of its structure.

c. Homologue of the homologous series with the general formula CnH2n.

Solution 29

a. Ethanol

b. Ethanoic acid

c. Ethene

Question 30

Give the correct IUPAC name and the functional group for each of the compounds whose structural formulae are given below:

a. 

   

 

b. 

 

Solution 30

a. Propanal

b. Propanol

Chapter 12 - Organic Chemistry Excercise Ex. 12C

Question 1

Write : (a) molecular formula , (b) electron dot formula and (c) structural formula of ethene .(Ethylene)

Solution 1

(a) The molecular formula of ethene is C2H4

(b) Electron dot formula of ethene is:

(c) Structural formula of ethene:

Question 2

The molecules of alkene family are represented by a general formula CnH2n.Answer The following :

(a) What do n and 2n signify?

(b) What is the name of alkene when n=4?

(c) What is the molecular formula of alkene when n=4?

(d) What is the molecular formula of the alkene if there are ten H atoms in it?

(e) What is the structural formula of the third member of the alkene family?

(f) Write the molecular formula of lower and higher homologus of an alkene which contains four carbon atoms.

Solution 2

(a) n signifies the number of carbon atoms and 2n signifies the number of hydrogen atoms.

(b) The name of alkene when n=4 is Butene.

(c) The molecular formula of alkene when n=4 is C4H8.

(d) The molecular formula of alkene when there are 10 H atom in it C5H10.

(e) The structural formula of the third member of alkene is

(f) Lower homologus of alkene which contain four carbons is C3H6.

Higher homologus of alkene which contain four carbons is C5H10.

Question 3

Distinguish between the saturated hydrocarbon ethane and the unsaturated hydrocarbon ethene by drawing their structural formulae.

Solution 3

Ethane

Ethene

It has carbon -carbon single bond.

It has carbon-carbon double bond

It is saturated.

It is unsaturated

Alkanes undergo substitution reaction.

Alkenes undergo addition reaction.

Question 4

Draw the structure of isomers of butane and write their IUPAC names.

Solution 4

There are two isomers are possible for butane:

Question 5

Give a balanced equation for the lab. Preparation of ethylene. How is the gas collected?

Solution 5

Balanced Equation of ethylene:

CH3-CH2OH + H2SO4 CH3-CH2HSO4+H2O

CH3-CH2HSO4CH2=CH2

The gas is collected by downward displacement of water.

Question 6

How is ethene prepared by:

(a) Dehydrohalogenation reaction?

(b) Dehydration reaction?

Give equations and name the products formed.

Solution 6

(a) Dehydrohalogenation reaction:

C2H5Cl + KOH(alc.and hot) C2H4 + KCl + H2O

Ethene

(b) Dehydration reaction:

C2H5OH C2H4+H2O

Ethene

Question 7

Ethylene when reacts with halogens (chlorine and bromine) form saturated products. Name them and write balanced equations.

Solution 7

Chlorine and bromine are added to the double bond of ethene to form saturated ethylene chloride and ethylene bromide respectively.

CH2 = CH2 + Cl2 CH2(Cl)-CH2(Cl)

1,2-dichloro ethane

 

CH2 = CH2 + Br2 CH2(Br)-CH2(Br)

1,2-dibromo ethane

 

Question 8

Give the conditions and the main product formed by hydrogenation of ethylene.

Solution 8

When ethene and hydrogen are passed over finely divided catalyst such as platinum or palladium at ordinary temperature or nickel at 200o C, the two atom of hydrogen molecule are added to the unsaturated molecule, which thus becomes a saturated one.

 

C2H4 +H2 C2H6

Question 9

Convert ethanol into ethene using

(a) Solid dehydrating agent

(b) Hot conc. H2SO4

Give only balanced equations.

Solution 9

Conversion of ethanol to ethene by using

(a) Solid dehydrating agent:

 

(b) Hot conc. H2SO4:

Question 10

Write the following properties of ethene:

(a) Physical state

(b) Odour

(c) Density as compared to air

(d) Solubility

Solution 10

(a) Physical state: Ethene is a colourless and inflammable gas.

(b) Odour: It has faint sweetish odour.

(c) Density as compared to air: It has density less than one hence it is lighter than air.

(d) Solubility: It is sparingly soluble in water but highly soluble in organic solvents like alcohol, ether and chloroform.

Question 11

How would you convert:

(a) Ethene into 1,2-dibromoethane

(b) Ethene into ethyl bromide

Solution 11

(a) Ethene into 1, 2 -dibromoethane: Ethene reacts with bromine at room temperature to form saturated ethylene chloride.

CH2=CH2 + Br2 CH2(Br)-CH2(Br)

1,2-dibromo ethane

(b) Ethene into ethyl bromide: When ethene is treated with HBr bromoethane is formed.

CH2=CH2 + HBr CH3-CH2Br

Ethyl bromide

Question 12

Give balanced equation when:

(a) Ethene is burnt in excess of oxygen

(b) Ethene reacts with chlorine

(c) Ethene combines with Hydrogen chloride

(d) A mixture of ethene and hydrogen is passed over nickel at 2000C.

Solution 12

(a) C2H4+3O2 2CO2 +2H2O + heat

(b) CH2=CH2+Cl2 CH2(Cl)-CH2(Cl)

(c) CH2=CH2 + HCl CH3-CH2-Cl

(d) C2H4 +H2 C2H6

Question 13

Give the formula and names of A, B ,C and D in the following equations:

(a) CH4ABCD

(b) C2H2ABCD

(c) C2H4 +B C2H6

Solution 13

(a) CH4CH3ClCH2Cl2CHCl3CCl4

A= monochloromethane

B= dichloromethane

C=Trichloromethane

D=Tetrachloromethane

(b) C2H2C2H4C2H6C2H5BrC2H4Br

A= Ethene

B=ethane

C=bromoethane

D=dibromoethane

(c) C2H4 +H2C2H6

B= hydrogen

Question 14

Write the name and formula of the productformed in each case below:

(a) C2H4 +Cl2 ______

(b) C2H5Br +KOH (alc.) ______

(c) CH2=CH2 _______

(d) CH2=CH2+HBr _______

Solution 14

(a) C2H4 +Cl2 CH2(Cl)-CH2(Cl)

1,2- dichloro ethane

(b) C2H5Br +KOH (alc.) C2H4 +KBr +H2O

Ethane

(c) CH2=CH2 CH2(OH)-CH2(OH)

1,2- Ethanediol

(d) CH2=CH2+HBr CH3-CH2Cl

chloroethane

Question 15

What do you observe when ethylene is passed through alkaline KMnO4 solution?

Solution 15

When ethylene is passed through alkaline KMnO4 solution 1, 2-Ethanediol is formed. The Purple color of KMnO4 decolorizes.

 

CH2=CH2+H-O-H +[O] CH2(OH)-CH2(OH)

Cold alkaline

KMnO4 solution

Question 16

Name three compounds formed by ethylene and give the use of these compounds.

Solution 16

Three compounds formed by ethylene are:

 

Polythene

Ethanol

Epoxyethane

 

Uses of above compounds:

 

Polythene is used as carry bags.

Ethanol is used as a starting material for other products, mainly cosmetics and toiletry preparation.

Epoxyethane is used in the manufacture of detergents.

Chapter 12 - Organic Chemistry Excercise Ex. 12D

Question 1

What are the sources for alkynes? Give the general formula of alkynes.

Solution 1

Natural gas and Petroleum are sources for alkynes.

The general formula of alkynes are:

CnH2n-2

Question 2

Give an example of isomers shown by triple bond hydrocarbon (alkynes) and write its IUPAC name.

Solution 2

Butyne is an example, its isomers are:

IUPAC name: But-2-yne But-1-yne

Question 3

How is acetylene prepared in the laboratory?

(a) Draw diagram

(b) Give equation

(c) How is pure dry gas collected?

Solution 3

(a) Diagram of acetylene preparation:

(b) CaC2 +2H2O Ca(OH)2 +C2H2

(c) The pure dry gas is collected by downward displacement of water, since it is insoluble in water.

Question 4

Give the method of preparation of ethyne by 1,2-dibromoethene.

Solution 4

When 1,2 -dibromoethane is boiled with alcoholic potassium hydroxide ,ethyne is formed.

Question 5

Name the hydrocarbon which:

(a) Is a tetrahedral molecule

(b) Is a planar molecule

(c) Is a linear molecule

(d) Forms a red precipitate with ammoniacal solution of copper (I) chloride

(e) Is known as paraffin

(f) Is known as olefin

(g) A compound which will give acetylene (ethene) gas when treated with water.

Solution 5

(a) The hydrocarbon which is tetrahedral is Methane.

(b) The hydrocarbon which is planar molecule is ethene.

(c) The hydrocarbon which is a linear molecule is Ethyne.

(d) The hydrocarbon which forms a red precipitate with ammoniacal solution of copper chloride is acetylene.

(e) Alkanes are also called as paraffin.

(f) Alkenes are also called olefin.

(g) Calcium carbide

Question 6

Classify the following compounds as alkanes, alkenes and alkynes.

C3H4,C3H8, C5H8, C3H6

Solution 6

The following compounds can be classified as:

C3H4:- Alkynes

C3H8:- Alkanes

C5H8:- Alkynes

C3H6:- Alkenes

Question 7

Give a chemical test to distinguish between

(a) Saturated and unsaturated compounds.

(b) Ethane and ethene

(c) Ethene (ethylene) and ethyne (acetylene)

Solution 7

Chemical test to distinguish :

(b) Ethane and ethene:

 

S.No.

Test

Ethane

Ethene

1.

On adding a few drops of bromine solution in carbon tetrachloride to the hydrocarbon

No change is observed

The reddish brown colour gets decolorized

2.

On adding a few drops of alkaline potassium permanganate (purple colour) to the hydrocarbon

No change is observed

The purple colour fades.

 

 

(c) Ethene and ethyne:

S.No.

Test

Ethene

Ethyne

1.

On adding a few drops of ammonical cuprous chloride to the hydrocarbon

No change is observed

Red precipitate of copper acetylide is formed

2.

On adding ammonical silver nitrate

No observation

White precipitate of silver acetylide is formed.

 

Question 8

Compound X bubbled through bromine dissolved in CCl4

(a) Draw the structure of X.

(b) State your observation during the reaction.

Solution 8

(a) HC≡CH

(b) Brown colour of CCl4 disappeared due to formation of addition product, i.e. 1, 2-dibromo ethane.

Question 9

Give balanced equations for the following conversations.

(a) An alkene to an alkane

(b) An alkene to an alcohol

(c) An alkyne to a alkene

Solution 9

(a) An alkene to an alkane

(b) An alkene to an alcohol

(c) An alkyne to an alkene

Question 10

Name the products formed and write an equation when ethyne is added to the following in an inert solvent:

(a) Chlorine

(b) Bromine

(c) Iodine

(d) hydrogen

(e) excess of hydrochloric acid

Solution 10

(a) Ethyne in an inert solvent of carbon tetrachloride adds chlorine to change into 1,2-dichloro ethene with carbon-carbon double bond, and then to an 1,1,2,2-tetrachloro ethane with carbon-carbon single bond.

C2H2C2H2Cl2C2H2Cl4

1,2-dichloro ethene1,1,2,2 -tetrachloro ethane

 (b) Ethyne in an inert solvent of carbon tetrachloride adds bromine to change into 1,2-dibromo ethene and then to 1,1,2,2 -tetrabromo ethane .

 C2H2C2H2Br2C2H2Br4

(c) Iodine reacts slowly in the presence of alcohol to form di-iodo ethene

CHCH +I2 ICH=CHI

1,2-di-iodoethene

(d) In the presence of nickel, platinum or palladium ethyne change to ethene and then to ethane.

CHCH CH2=CH2CH3-CH3

(e) begin mathsize 12px style table attributes columnalign left end attributes row cell straight C subscript 2 straight H subscript 2 plus HCl rightwards arrow with blank on top CH subscript 2 CHCl rightwards arrow with plus HCl on top CH subscript 3 CHCl subscript 2 end cell row cell ethyne space space Chloro space space ethane space space space 1 comma 1 minus dichloro space ethane end cell end table end style

Chapter 12 - Organic Chemistry Excercise Ex. 12E

Question 1

(a) What are alcohols? State their sources.

(b) Give general formulae of monohydric alcohol.

Solution 1

(a) Alcohols are the hydroxyl derivatives of alkanes and are formed by replacing one or more hydrogen atoms of the alkane with OH group.

Methanol is obtained from destructive distillation of wood while ethanol is obtained from fermentation of sugar.

(b) General formula of monohydric alcohol:

CnH2n+ 1OH

Question 2

Give the

(a) Dot diagram of first member of alcohol,

(b) Abbreviated formula of third member of alcohol

(c) Structure of second member of the alcohol group

(d) Structure of alcohol with 4 carbon atoms

Solution 2

(a) Dot diagram

 

 

(b) Abbreviated formula

C2H5OH

 

(c) Structure:

 

Question 3

State the method of preparation of ethanol:

(a) By hydrolysis of ethene

(b) By hydrolysis of ethyl bromide

Solution 3

(a) By hydrolysis of ethene: When concentrated sulphuric acid is added to ethene at a temperature of 80oC and pressure of 30 atm. ethyl hydrogen sulphate is produced. Ethyl hydrogen sulphate on hydrolysis with boiling water gives ethanol.

C2H4 +H2SO4 C2H5HSO4

C2H5HSO4 + H2O C2H5OH +H2SO4

 

(b) By hydrolysis of alkyl halide: Alcohols can be prepared by the hydrolysis of alkyl halide with a hot dilute alkali.

C2H5Cl + KOH C2H5OH +KCl

Question 4

Halo alkanes react with alkalies to produce alcohol. Give the equation for the preparation of the second member of the homologous series of alcohol. State under what condition the reaction occurs.

Solution 4

When an aqueous solution of a strong alkali like NaOH is treated with chloroethane, it gives ethyl alcohol.

Question 5

(a)How do the boiling point and melting point change in the homologous series of alcohols?

(b) Name the product formed when ethanol reacts with acetic acid. Give an equation

(c) What is the name given to this type of reaction?

Solution 5

(a)The melting and boiling point of the successive members of the homologous series of alcohols increase with the increase in molecular mass.

(b)When ethanol reacts with acetic acid ethyl acetate is formed.

 C2H5OH + CH3COOH CH3COOC2H5 + H2O

(c) This reaction is known as esterification reaction.

Question 6

Complete and balance the following equations. State the conditions wherever necessary.

(a) CHCH + H2 _________+ H2 ________

(b) C2H4 + Cl2 __________

(c) C2H4 + HCl_________

(d) CaC2 + H2O _________

(e) C2H2 + Br2 __________

(f) C2H5OH  ________

Solution 6

(a) CHCH +H2 CH2=CH2 +H2 CH3-CH3

(b) C2H4 + Cl2 CH2(Cl)-CH2(Cl)

(c) C2H4 + HCl CH3-CH2Cl

(d) CaC2 + 2H2O C2H2+Ca(OH)2

(e) C2H2 + Br2 H(Br)C=C(Br)H

(f) C2H5OH CH3CHO

Question 7

What is the effect of ethanol on human body?

Solution 7

Ethanol affects that part of the brain which controls our muscular movements and then gives temporary relief from tiredness. But it damages the liver and kidney too.

Question 8

How are the following obtained

(a) Absolute alcohol

(b) Spurious alcohol

(c) Methylated spirit?

Solution 8

(a) Absolute alcohol: Absolute alcohol may be obtained by distilling moist alcohol with benzene. The mixture of water and benzene distills off and anhydrous alcohol is left behind.

(b) Spurious alcohol: It is made by improper distillation. It contains large portions of methanol in a mixture of alcohols.

(c) Methylated spirit: Methylated spirit or denatured alcohol is ethyl alcohol with 5%methyl alcohol, a coloured dye and some pyridine.

Question 9

Name the products formed and give appropriate chemical equations for the following:

(a) Sodium reacting with ethyl alcohol

(b) Ethanol oxidized by acidified potassium dichromate

Solution 9

(a) Sodium reacting with ethyl alcohol:

2C2H5OH + 2Na 2C2H5ONa + H2

When sodium reacts with ethyl alcohol hydrogen is evolved with formation of sodium ethoxide.

 

(b) Ethanol oxidized by K2Cr2O7:

C2H5OHCH3CHO+H2OCH3COOH

Alcohols gets oxidized and get converted into ethanal and then into acetic acid.

Question 10

Give the trivial (common) names and IUPAC names of the following:

(a) C3H6

(b) C2H4

(c) C2H2

(d) CH3OH

(e) C2H5OH

Solution 10

S No

Formula

Common Name

IUPAC

1

C3H6

Propylene

Propene

2

C2H4

Ethylene

Ethene

3

C2H2

Acetylene

Ethyne

4

CH3OH

Methyl alcohol

Methanol

5

C2H5OH

Ethyl alcohol

Ethanol

Question 11

Ethanol can be oxidized to Ethanoic acid. Write the equation and name the oxidizing agent.

Solution 11

C2H5OHCH3CHO+H2OCH3COOH

The oxidizing agents that can be used are potassium dichromate and potassium permanganate.

Question 12

Name an Organic compound which is:

(a) Used for illuminating country houses

(b) Used for making a household plastic material

(c) Called 'wood spirit'

(d) Poisonous and contain OH group

(e) Consumed as a drink

(f) Made from water gas

(g) solvent for ethanol.

Solution 12

(a) Used for illuminating country houses : Ethyne

(b) Used for making a household plastic material: ethyne

(c) Called 'wood spirit' : Methanol

(d) Poisonous: Methanol

(e) Consumed as a drink: Ethanol

(f) Made from water gas: Methanol

(g) Methanol

Chapter 12 - Organic Chemistry Excercise Ex. 12F

Question 1

What are carboxylic acids? Give their general formula?

Solution 1

An organic compound containing the carboxyl group(COOH) is known as carboxylic acid.

The general formula: CnH2n+1COOH

Question 2

Write the names of:

(a) First three members of carboxylic acid series

(b) Three compounds which can be oxidized directly, or in stages to produce acetic acid

Solution 2

(a) First three members of carboxylic acids are:

Methanoic acid

Ethanoic acid

Propanoic acid

(b) Three compounds that can be oxidized directly or in stages to produce acetic acid are:

Ethanol

Acetylene

Ethanal

Question 3

Give the structural formula and IUPAC name of acetic acid. What is glacial acetic acid?

Solution 3

Structural formula of acetic acid:

IUPAC name of acetic acid is:

Ethanoic acid

Glacial acetic acid is the pure form of acetic acid. It does not contain water.

Question 4

Vinegar is greyish in colour with particular taste. Explain.

Solution 4

Vinegar commonly called Sirka is a dilute solution of acetic acid. The presence of colouring matter gives it a greyish colour while the presence of some other organic acids and organic compounds impart it the usual taste and flavour.

Question 5

Complete:

(a) Vinegar is prepared by the bacterial oxidation of ______.

(b) The organic acid present in vinegar is __________.

(c) The next higher homologue of Ethanoic acid is ______.

Solution 5

(a) Ethanol

(b) Acetic acid

(c) Propanoic acid

Question 6

How is acetic acid prepared from

(a) ethanol

(b) acetylene?

Solution 6

(a)It is prepared in the lab by the oxidation of ethanol with acidified potassium dichromate.

C2H5OHCH3CHO CH3COOH

(b)Acetylene is first converted to acetaldehyde by passing through 40% H2SO4 at 60°C in the presence of 1% HgSO4.

The acetaldehyde is then oxidised to acetic acid in the presence of catalyst manganous acetate at 70°C.

C2H2  + H2begin mathsize 14px style rightwards arrow from HgSO subscript 4 to space space space space straight H 2 SO 4 left parenthesis dil right parenthesis space space space space of end style CH3CHO

CH3CHO + O2 begin mathsize 14px style rightwards arrow from space space space space Catalyst space space space space space to space space space increment space space space space of end style 2CH3COOH

 

Question 7

What do you notice when acetic acid reacts with

(a) Litmus

(b) Metals

(c) Alkalies

(d) alcohol

Solution 7

(a) When acetic acid reacts with litmus it turns blue litmus red.

(b) When acetic acid reacts with metals hydrogen is evolved.

2CH3COOH + Zn (CH3COO)2Zn + H2

(c) When acetic acid reacts with alkalies it forms salt

CH3COOH + NaOH CH3COONa + H2O

(d) Acetic acid reacts with alcohols forming esters

CH3COOH + C2H5OH CH3COOC2H5 + H2O

Question 8

Acetic acid is a typical acid. Write the equation in each case for its reaction with

(a) Metal

(b) A base/alkali

(c) A carbonate

(d) A bicarbonate

Solution 8

(a) 2CH3COOH + Zn (CH3COO)2Zn + H2

(b) CH3COOH + NaOH CH3COONa + H2O

(c) 2CH3COOH + Na2CO3 2CH3COONa +H2O+ CO2

(d) CH3COOH + NaHCO3 CH3COONa + H2O +CO2

Question 9

What do you observe when acetic acid is added to:

(a) Sodium bicarbonate

(b) Ethyl alcohol in the presence of sulphuric acid

(c) Neutral FeCl3 solution

Solution 9

(a) When acetic acid is added to sodium bicarbonate, carbondioxide is liberated.

CH3COOH + NaHCO3 CH3COONa + H2O +CO2

(b) When acetic acid is added to ethyl alcohol in presence of sulphuric acid ester (ethyl acetate) is formed.

CH3COOH + C2H5OH CH3COOC2H5 + H2O

(c) When acetic acid is added to neutral FeCl3, wine red color is produced.

Question 10

Name :

(a) Compound formed when acetic acid and ethanol react together

(b) Reducing agent used to convert acetic acid into ethanol

(c) Substance used to change acetic acid to acetic anhydride

Solution 10

(a) When acetic acid and ethanol react it results in the formation of ethyl acetate.

(b) Lithum aluminium hydride(LiAlH4) is used to convert acetic acid to ethanol.

(c) Phosphorous pentoxide(P2O5) is heated along with acetic acid to form acetic anhydride.

Chapter 12 - Organic Chemistry Excercise Ex. 12B

Question 1

State the sources of alkanes.

Solution 1

Sources of alkane:

The principal sources of alkanes are Natural gas and petroleum.

Question 2

Methane is a green house gas. Comment.

Solution 2

Methane is a primary constituent of natural gas. It absorbs outgoing heat radiation from the earth, and thus contributes to the green house effect and so it is considered as a green house gas.

Question 3

Give the general formula of alkanes.

Solution 3

The general formula of alkane is :

CnH 2n+2

Question 4

Draw the structures of isomers of

(a) Butane (b) Pentane

Write the IUPAC and common names of these isomers

Solution 4

(a)The structures of isomers of butane are:

(i)

Common name:- n-Butane

IUPAC name:- Butane

(ii)

Common name:-iso butane

IUPAC name:- 2-methyl propane

(b) The structures of isomers of Pentane are:

(i)

Common name: n-pentane

IUPAC name:- Pentane

(ii)

Common name:- iso pentane

IUPAC name:- 2-methyl butane

(iii)

Common name- neo pentane

IUPAC name:- 2,2-dimethyl propane

Question 5

Write the

(a) Molecular formula

(b) Electron dot formula and

(c) Structural formula of methane and ethane

Solution 5

For methane:

(a) Molecular formula is CH4

(b) Electron dot formula

(c) Structural formula

For ethane:

(a) Molecular formula is :- C2H6

(b) Electron dot formula:

(a) Structural Formula:

Question 6

How is

(a) Methane and

(b) Ethane prepared in the laboratory

Solution 6

(a) Laboratory preparation of methane:

When the mixture of sodium ethanoate and soda lime is taken in a hard glass test tube and heated, the gas evolved is methane. It is collected by downward displacement of water.

CH3COONa+NaOHNa2CO3+CH4

(b) Laboratory preparation of ethane:

When the mixture of sodium propionate and soda lime is taken in the boiling tube and heated the ethane gas is evolved. It is also collected by downward displacement of water.

C2H5COONa+NaOHNa2CO3+C2H6

Question 7

How are methane and ethane prepared from methyl iodide and ethyl bromide?

Solution 7

When methyl iodide is reduced by nascent hydrogen at ordinary room temperature then methane is formed.

CH3I+2[H] CH4+HI

When bromoethane is reduced by nascent hydrogen at ordinary room temperature then ethane is produced.

C2H5Br+2[H] C2H6+HBr

Question 8

What is substitution reaction? Give the reaction of chlorine with ethane and name the product formed?

Solution 8

A reaction in which one atom of a molecule is replaced by another atom (or group of atoms)is called a substitution reaction.

When ethane reacts with chlorine

C2H6 +Cl2 C2H5Cl + HCl

Chloroethane

C2H5Cl + Cl2C2H4Cl2+HCl

Dichloroethane

C2H4Cl2 +Cl2 C2H3Cl3+HCl

Trichloroethane

C2H3Cl3 + Cl2 C2H2Cl4 + HCl

Tetrachloroethane

C2H2Cl4 +Cl2 C2HCl5 +HCl

Pentachloroethane

C2HCl5 +Cl2 C2Cl6 + HCl

Hexachloroethane

Question 9

Name the compounds formed when methane burns in

(a) Sufficient air(b) insufficient air

Give a balanced equation

Solution 9

(a) Sufficient air: When methane burns in sufficient air, then carbon dioxide and water vapors are formed.

CH4 + 2O2 CO2+2H2O

(b) Insufficient air: When methane burns in insufficient air , then carbon monoxide and water is formed.

2CH4 + 3O2 2CO + 4H2O

Question 10

Write the names and formula of the products formed when

(a) Methane and (b) ethane , reacts with :

(i) Chlorine (ii) bromine

Write the chemical equations.

Solution 10

(a)

(i) When methane reacts with chlorine in the presence of sunlight or UV light, it undergoes substitution reaction to form Tetrachloromethane.

(ii) When it reacts with bromine it forms Tetrabromomethane

CH4 + Br2CH3Br + HCl

CH3Br + Br2CH2Br2 + HCl

Dibromomethane

CH2Br2 + Br2CHBr3 + HCl

Tribromo methane

CHBr3 + Br2CBr4 + HCl

Tetrabromomethane

(b)

(i) When ethane reacts with chlorine it forms hexachoroethane.

C2H6 +Cl2 C2H5Cl + HCl

Chloroethane

C2H5Cl + Cl2 C2H4Cl2+HCl

Dichloroethane

C2H4Cl2 +Cl2 C2H3Cl3+HCl

Trichloroethane

C2H3Cl3 + Cl2 C2H2Cl4 + HCl

Tetrachloroethane

C2H2Cl4 +Cl2 C2HCl5 +HCl

Pentachloroethane

C2HCl5 +Cl2 C2Cl6 + HCl

Hexachloroethane

(ii) When ethane reacts with bromine it forms Hexabromoethane

C2H6 +Br2 C2H5Br + HBr

Bromoethane

C2H5Br + Br2 C2H4Br2+HBr

Dibromoethane

C2H4Br2 +Br2 C2H3Br3+HBr

Tribromoethane

C2H3Br3 + Br2 C2H2Br4 + HBr

Tetrabromoethane

C2H2Br4 +Br2 C2HBr5 +HBr

Pentabromoethane

C2HBr5 +Br2 C2Br6 + HBr

HexaBromoethane

Question 11

Name the compound prepared from

(a) Sodium propionate

(b) Methyl iodide

(c) Ethyl bromide

Write the balanced equation for the same

Solution 11

(a) Ethane is prepared from sodium propionate.

C2H5COONa+NaOHNa2CO3+C2H6

(b) Methane is prepared from methyl iodide.

CH3I+2[H] CH4+HI

(c) Ethane is prepared from ethyl bromide.

C2H5Br+2[H] C2H6+HBr

Question 12

Write the equation for the complete combustion of

(i) methane (ii) ethane.

Solution 12

(i) 

(ii)

Question 13

What is pyrolysis or cracking? Explain with an example.

Solution 13

The decomposition of a compound by heat in the absence of air is called Pyrolysis. When pyrolysis occurs in alkanes, the process is termed cracking.

For example:

Alkanes on heating under high temperature or in the presence of a catalyst in absence of air broken down into lower alkanes, alkenes and hydrogen.

2CH4 HC?CH + 3H2

Question 14

Convert

(a) Methane into chloroform

(b) Sodium acetate into methane

(c) Methyl iodide into ethane

(d) Aluminium carbide into methane

Solution 14

(a) Methane into chloroform

CH4+Cl2 CH3Cl+HCl

CH3Cl+Cl2 CH2Cl2+HCl

CH2Cl2+Cl2 CHCl3+HCl

(b) Sodium acetate into methane

CH3COONa+NaOHNa2CO3+CH4

(c) Methyl iodide into ethane

2CH3I +2NaCH3-CH3+2NaI

(d) Aluminium carbide into methane

Al4C3 +12H2O 3CH4+4Al(OH)3

Question 15

Give three uses of:

(a) Methane

(b) ethane

Solution 15

(a) Methane: Three uses of methane are:

(i) Methane is a source of carbon monoxide and hydrogen

(ii) It is used in the preparation of ethyne, methanal, chloromethane, carbon tetrachloride.

(iii) It is employed as a domestic fuel.

(b) Ethane:

Three uses of ethane are:

(i) It is used in the preparation of ethene, ethanol, and ethanol.

(ii) It forms ethyl chloride, which is used to make tetraethyllead.

(iii) It is also a good fuel.

Question 16

Under what conditions does ethane get converted to:

(a) Ethyl alcohol

(b) Acetaldehyde

(c) Acetic acid

Solution 16

(a) When a mixture of ethane and oxygen is compressed to about 120atm pressure and passed over copper tubes at 475K, ethyl alcohol is formed.

2C2H6 +O22C2H5OH

(b) When mixture of ethane and oxygen is passed through heated molybdenum oxide, the mixture is oxidized to Acetaldehyde.

C2H6 +O2 CH3CHO+H2O

(c) Ethanol formed from ethane gets oxidized to acetic acid.

2C2H6 +O22C2H5OH

C2H5OH + O2 CH3COOH+H2O

Question 17

Using appropriate catalysts, ethane can be oxidized to an alcohol, an aldehyde and an acid. Name the alcohol, aldehyde and acid formed when ethane is oxidized.

Solution 17

Ethane can be oxidized as follows:

When a mixture of ethane and oxygen in the ratio 9:1 by volume is compressed to about 120 atm pressure and passed over copper tubes at 475K, ethyl alcohol is formed.

2C2H6 + O2 2C2H5OH

When a mixture of ethane and oxygen is passed through heated MoO, the mixture is oxidized to ethanal.

C2H6+ O2 CH3CHO + H2O

When a manganese based catalyst is used 100oC, ethane can be oxidized to ethanoic acid.

2C2H6 + 3O2 2CH3COOH + 2H2O

Chapter 12 - Organic Chemistry Excercise Misc. Ex.

Question 1

(a) Write an equation for the laboratory preparation of

  1. An unsaturated hydrocarbon from calcium carbide.
  2. An alcohol from ethyl bromide.

(b) What would you see, when ethyne is bubbled through a solution of bromine in carbon tetrachloride?

(c) Name the addition product formed between ethene and water

Solution 1

  (a)  i. begin mathsize 12px style table attributes columnalign left end attributes row cell CaC subscript 2 plus 2 straight H subscript 2 straight O rightwards arrow with blank on top Ca left parenthesis OH right parenthesis subscript 2 plus straight C subscript 2 straight H subscript 2 straight H upwards arrow end cell row cell Calcium space space space space space space space space space space space space space space space space space space Calcium space acetylene end cell row cell carbide space space space space space space space space space space space space space space space space space space space hydroxide end cell end table end style

ii. begin mathsize 12px style table attributes columnalign left end attributes row cell straight C subscript 2 straight H subscript 5 Br plus NaOH rightwards arrow with boil on top straight C subscript 2 straight H subscript 5 OH plus NaBr end cell row cell Ethyl space left parenthesis aq. right parenthesis space space space space space space space space space space space space space space space space space ethyl end cell row cell bromide space space space space space space space space space space space space space space space space space space space space space alcohol end cell end table end style

(b) When bromine in carbon tetrachloride is added to ethyne, the orange colour of the bromine disappears due to the formation of the colourless ethylene bromide.

(c) Water reacts with ethene to form ethanol.

CH2=CH2 +H2OC2H5OH


 
 
  

Question 2

Ethanol can be converted into ethene which can be changed into ethane. Choose the correct word or phrase from the brackets to complete the following sentences.

(a) The conversion of ethanol into ethene is an example of _____ (Dehydration , dehydrogenation)

(b) Converting ethanol into ethene requires the use of ___ (Conc.HCl, Conc. HNO3, conc. H2SO4).

(c) The conversion of ethene into ethane is an example of _____ (hydration, hydrogenation).

(d) The catalyst used in the conversion of ethene into ethane is commonly ____ (iron, nickel, cobalt).

Solution 2

(a) The conversion of ethanol into ethene is an example ofDehydration.

(b) Converting ethanol into ethene requires the use of Conc. H2SO4.

(c) The conversion of ethene into ethane is an example of hydrogenation.

(d) The catalyst used in the conversion of ethene into ethane is commonly nickel.

Question 3

Give reasons:

(a) Ethyne is more reactive than ethene.

(b) Ethene is more reactive then ethane.

(c) Hydrocarbons are excellent fuels.

Solution 3

(a) Ethyne is a highly reactive compound than ethene because of the presence of a triple bond between its two carbon atoms.

(b) Ethene is a highly reactive compound than ethane because of the presence of a double bond between its two carbon atoms.

(c) Hydrocarbons such as alkanes undergo combustion reactions with oxygen to produce carbon dioxide and water vapour. Alkanes are flammable which makes them excellent fuels.

Methane for example is the principal component of natural gas.

CH4 + 2O2 → CO2 + 2H2O

Question 4

a. Write balanced equations:

 i. When butane is burnt in oxygen.

 ii. Preparation of ethylene from ethyl alcohol.

b. 

 i. Convert ethane to acetic acid

 ii. Convert acetylene to ethane

 iii. Convert acetic acid to ethyl alcohol

 iv. Convert acetic acid to ethyl acetate

Solution 4

a. 

i. 

ii. 

b. 

i.   

ii. 

  

iii. 

 

iv. 

 

Question 5

Write the equations for the following lab preparations:

(a) Ethane from sodium propionate

(b) Ethene from Iodoethane

(a)Ethyne from Calcium carbide

(b)Methanol from Iodoethane

Solution 5

(a)Ethane from sodium propionate

C2H5COONa + NaOH Na2CO3 + C2H6

 

(b)Ethene from iodoethane

C2H5 I +KOH(alcoholic) C2H4 +KI + H2O

 

(c)Ethyne from calcium carbide

CaC2 +2H2O Ca(OH)2 + C2H2

 

(d)Methanolfrom iodoethane

CH3I + NaOH CH3OH + NaI

Question 6

(a) Write the equation for the preparation of carbon tetrachloride from methane.

(b) Draw the structure formula of ethyne.

(c) How is the structure of alkynes different from that of alkenes?

Solution 6

(a)Preparation of carbon tetrachloride from methane:

 

CH4+Cl2 CH3Cl +HCl

CH3Cl + Cl2 CH2Cl2 +HCl

CH2Cl2 +Cl2 CHCl3 +HCl

CHCl3 + Cl2 CCl4 +HCl

 

(b)Structural formula of ethyne:

 

 

(c)Alkynes contain triple bond where as alkenes contain double bond.

Question 7

Fill in the blanks with correct words from the brackets:

Alkenes are the (a) _______ (analogous/homologous) series of (b ) ______ (saturated /unsaturated) hydrocarbons. They differ from alkanes due to presence of (c) _______ (double/ single) bonds. Alkenes mainly undergo (d) ______ (addition/ substitution) reactions.

Solution 7

Alkenes are the (a) homologous series of (b) unsaturated hydrocarbons. They differ from alkanes due to presence of (c)single bonds. Alkenes mainly undergo (d) addition reactions.

Question 8

The organic compound which undergoes substitution reaction is (v)……….(C2H2, C2H4, C10H18, C2H6)

Solution 8

The organic compound which undergoes substitution reaction is C2H6.

Question 9

(a) Draw the structural formulae of the two isomers of Butane. Give the correct IUPAC name of each of the isomer.

(b) State one use of acetylene.

Solution 9

(a) Structural formulae of isomers ofButane are:

Butane2-methyl propane

 

(b) Use of acetylene:

 

For Oxy-acetylene welding at very high temperatures.

Question 10

Copy and complete the following table which relates to three homologous series of hydrocarbons:

General Formula

CnH2n

CnH2n-2

CnH2n+2

IUPAC name of the homologous series

     

Characteristics bond type

   

Single bonds

IUPAC name of the first member of the series

     

Type of reaction with chlorine

 

Addition

 
Solution 10

The homologous series of hydrocarbons are:

 

General Formula

CnH2n

CnH2n-2

CnH2n+2

IUPAC name of the homologous series

Alkenes

Alkynes

Alkanes

Characteristics bond type

Double bond

Triple Bond

Single Bond

IUPAC name of the first member of the series

Ethene

Ethyne

Methane

Type of reaction with chlorine

Addition

Addition

Substitution

 

Question 11

(a) Name the organic compound prepared by each of the following reactions:

(i) C2H5COONa +NaOH

(ii) CH3I +2H

(iii) C2H5Br +KOH (alcoholic solution)

(iv) CO + 2H2 (Zinc oxide catalyst)

(v) CaC2 + 2H2O

Solution 11

(i) C2H5COONa +NaOHNa2CO3 + C2H6

(ii) CH3I +2[H] CH4 +HI

(iii) C2H5Br + KOH C2H4 +KBr +H2O

(iv) CO + 2H2 CH3OH

(v) CaC2 +2H2O Ca(OH)2 +C2H2

Question 12

Write the equations for the following reactions:

(a) Calcium carbide and water

(b) Ethene and water (steam)

(c) Bromoethane and an aqueous solution of sodium hydroxide

Solution 12

(a) Calcium carbide and water:

CaC2 + 2H2O Ca(OH)2 + C2H2

(b) Ethene and water:

CH2=CH2 +H2O C2H5OH

(c) Bromoethane and aqueous solution of sodium hydroxide

C2H5Br +NaOH C2H5OH +NaBr

Question 13

A compound X when treated with an organic acid Y (having vinegar like smell) in the presence of the acid Z, forms a compound P which has fruity smell.

(a) Identify X, Y and Z

(b) Write structural formula of X and Y.

(c) What type of compound P is?

(d)Name the above reaction.

(e) If compound X and Y both have 2 carbon atoms. Write the reaction.

Solution 13

(a) X = Ethanol, C2H5OH

 Y = Acetic acid, CH3COOH

 Z = Conc. H2SO4

(b)  

(c) Compound P is an ester named ethyl acetate.

(d) Esterification

(e) 

Question 14

a. Which of the following statements is wrong about alkanes?

 i. They are all saturated hydrocarbons.

 ii. They can undergo addition as well as substitution reactions.

 iii. They are almost non-polar in nature.

 iv. On complete combustion, they give out carbon dioxide and water.

b. The organic compound obtained as the end product of the fermentation of sugar solution is

 i. Methanol

 ii. Ethanol

 iii. Ethane

 iv. Methanoic acid

c. Find the odd one out and explain:

 C3H8, C5H10, C2H6, CH4

d. Give chemical equations for

 i. The laboratory preparation of methane from sodium acetate.

 ii. The industrial preparation of methanol from water gas.

 iii. The reaction of one mole of ethene with one mole of chlorine gas.

 iv. The preparation of ethyne from 1, 2-dibromoethane.

e. State how the following conversions can be carried out:

 i. Ethyl chloride to ethyl alcohol

 ii. Ethyl chloride to ethene

 iii. Ethene to ethyl alcohol

 iv. Ethyl alcohol to ethene

f. 

 i. Define isomerism.

 ii. Give the IUPAC name of the isomer C4H10 which has a branched chain.

Solution 14

a. ii. They can undergo addition as well as   substitution reactions.

 

b. ii. Ethanol.

 

c. C5H10 is an alkene, while the rest are alkanes.

 

d.  

 

i. 

 

ii.

 iii.

iv.

 

e.  i. By treating ethyl chloride with aqueous KOH

 

 ii.  By heating ethyl chloride with alcoholic KOH

 

iii.  By passing ethene into conc. H2SO4 at 80°C and  high pressure

 iv.  By heating ethyl alcohol with conc. H2SO4 at 170°C

f.  

i. Isomerism: Compounds having the same molecular formula but different structural formulae are known as isomers, and the phenomenon is known as isomerism.

 

ii. The IUPAC name of the branched isomer of butane is 2-methyl propane

Question 15

a. An organic compound undergoes addition reactions and gives a red precipitate with ammoniacal cuprous chloride. Therefore, the organic compound could be

 i. Ethane

 ii. Ethene

 iii. Ethyne

 iv. Ethanol

b. An organic weak acid is

 i. Formic acid

 ii. Sulphuric acid

 iii. Nitric acid

 iv. Hydrochloric acid

c. The organic compound mixed with ethanol to make it spurious is

 i. Methanol

 ii. Methanoic acid

 iii. Methanal

 iv. Ethanoic acid

d. Draw the structural formula for each of the following:

 i. Ethanoic acid

 ii. But-2-yne

e. Compound A is bubbled through bromine dissolved in carbon tetrachloride and the product is CH2Br - CH2Br.

 i. Draw the structural formula of A.

 ii. What type of reaction has A undergone?

 iii. What is your observation?

 iv. Name (not formula) the compound formed when steam reacts with A in the presence of phosphoric acid.

 v. What is the procedure for converting the product of (e) (iv) back to A?

Solution 15

a. iii. Ethyne

b. i. Formic acid

c. i. Methanol

d. i.   

ii    

e.  

i.   

ii. Addition reaction

iii. Bromine solution gets decolourised

iv. Ethanol 

v. By heating it (ethanol) with concentrated sulphuric acid at 170°C

Question 16

a. The functional group present in acetic acid is

 i. Ketonic  - =C=O

 ii. Hydroxyl - OH

 iii. Aldehydic - CHO

 iv. Carboxyl - COOH

b. The unsaturated hydrocarbons undergo

 i. a substitution reaction

 ii. an oxidation reaction

 iii. an addition reaction

 iv. none of the above

c. The number of C-H bonds in ethane molecule is

 i. Four

 ii. Six

 iii. Eight

 iv. Ten

d. Choose the correct word/phrase from within the brackets to complete the following sentences:

 i. The catalyst used for conversion of ethene to ethane is commonly (nickel /iron/cobalt)

 ii. When acetaldehyde is oxidised with acidified potassium dichromate, it forms (ester/ethanol/ acetic acid)

 iii. Ethanoic acid reacts with ethanol in the presence of concentrated H2SO4 so as to form a compound and water. The chemical reaction which takes place is called (dehydration/hydrogenation/ esterification)

 iv. Write the equation for the reaction taking place between 1, 2-dibromoethane and alcoholic potassium hydroxide.

 v. The product formed when ethene gas reacts with water in the presence of sulphuric acid ………… (ethanol/ethanal/ethanoic acid)

e. Write balanced chemical equations for the following:

 i. Monochloroethane is hydrolysed with aqueous KOH.

 ii. A mixture of sodalime and sodium acetate is heated.

 iii. Ethanol under high pressure and low temperature is treated with acidified potassium dichromate.

 iv. Water is added to calcium carbide.

 v. Ethanol reacts with sodium at room temperature.

Solution 16

a. iv. Carboxyl - COOH

b. iii. An addition reaction

c. iii Six

d. 

i. Nickel

 ii.  Acetic acid

 iii. Esterification

 iv.   

  

 v.  Ethanol

 

e.  

i. 

ii.   

iii.   

iv.  CaC2 + 2H2O Ca(OH)2 + C2H2 

v. 2C2H5OH + 2Na 2C2H5ONa + H2 

Question 17

a. Give the structural formula for the following:

 i. Methanoic acid

 ii. Ethanol

 iii. Ethyne

 iv. Acetone

 v. 2-methyl propane

b. From the following organic compounds given below, choose one compound in each case which relates to the description [i] to [iv]:

[Ethyne, ethanol, acetic acid, ethene, methane]

 i. An unsaturated hydrocarbon used for welding purposes.

 ii. An organic compound whose functional group is carboxyl.

 iii. A hydrocarbon which on catalytic hydrogenation gives a saturated hydrocarbon.

 iv. An organic compound used as a thermometric liquid.

c.  

 i. Why is pure acetic acid known as glacial acetic acid?

 ii. Give a chemical equation for the reaction between ethyl alcohol and acetic acid.

Solution 17

a. i.

  

ii.

 

 

 iii.   

iv. 

 

 

v.

 

 

b.  i.  Ethyne

 ii.  Acetic acid

 iii. Ethene

 iv Ethanol

 

c. i. Pure acetic acid is called glacial acid because it forms an ice-like solid when cooled.

ii.   

Question 18

a.  

 i. Give a chemical test to distinguish ethene gas and ethane gas.

 ii. Identify the statement that is incorrect about alkanes:

A. They are hydrocarbons.

B. There is a single covalent bond between carbon and hydrogen.

C. They can undergo both substitution as well as addition reactions.

D. On complete combustion, they produce carbon dioxide and water.

b. Give the structural formulae for the following:

 i. An isomer of n-butane

 ii. 2-propanol

Solution 18

a. 

i. Ethene gas decolourises the purple colour of KMnO4, whereas ethane does not decolourise KMnO4 solution.

 ii. They can undergo both substitution as well as addition reactions.

b. 

 i. Isomer of n-butane: Isobutane

  

 ii. 2-propanol

 

Question 19

a. The IUPAC name of acetylene is

 i. propane

 ii. propyne

 iii. ethane

 iv. ethyne

b. Name the hydrocarbons containing the    functional group.

c. Give preparation of ethane from sodium propionate.

d. Distinguish ethane and ethene (using alkaline potassium permanganate solution).

e. Give the structural formula of the following:

 i. ethanol

 ii. 1-propanal

 iii. ethanoic acid

 iv. 1, 2, dichloroethane

f. Give preparation of ethanol from monochloroethane and aq. sodium hydroxide.

Solution 19

a. (iv) ethyne

b. Ketones

c.  

  

d. Ethene gas decolourises the purple colour of KMnO4, whereas ethane does not decolourise KMnO4 solution.

 

e. 

 i. Ethanol:

   

 ii. 1-propanal:

  

 iii. Ethanoic acid:

 

 iv. 1, 2-dichloroethane:

   

f.  

 The balanced chemical equation for the preparation

 of ethanol from monochloroethane and aqueous

 sodium hydroxide:

 C2H5-Cl + NaOH (aq.)   C2H5OH + NaCl

Question 20

(a) Give balanced chemical equations for the following conversions:

(i) Ethanoic acid to ethyl ethanoate

(ii) Calcium carbide to ethylene

(iii) Sodium ethanoate to methane

(b) Using their structural formula, identify the functional group by circling them:

(i) Dimethyl ether

(ii) Propanone

(c) Name the following:

(i) Process by which ethane is obtained from ethane

(ii) A hydrocarbon which contributes towards the greenhouse effect

(iii) Distinctive reaction that takes place when ethanol is treated with acetic acid

(iv) The property of elements by virtue of which atoms of the element can link to each other in the form of a long chain or ring structure

(v) Reaction when an alkyl halide is treated with alcoholic potassium hydroxide

Solution 20

(a)  

(i) Ethanoic acid to ethyl ethanoate

 CH3COOH + C2H5OH    CH3COOC2H5 + H2O

(ii) Calcium carbide to ethylene

 CaC2 + 2 H2O  Ca(OH)2 + CH º CH

(iii) Sodium ethanoate to methane

CH3COONa + NaOH   Na2CO3 + CH4

(b)  

(i) Dimethyl ether

   

(ii) Propanone 

 

(c) Name the following:

(i) Hydrogenation

(ii) Methane

(iii) Esterification 

(iv) Catenation

(v) Dehydrohalogenation 

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