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Chapter 12 - Organic Chemistry Exercise Intext 1

Question 1

(a) What are organic compounds?

(b) What is the Vital force theory? Why was it discarded?Solution 1

(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 2

(a) Name a few sources of organic compounds

(b) Give the various applications of organic chemistrySolution 2

(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 3

Organic chemistry plays a key role in all walks of life. DiscussSolution 3

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 4

Carbon shows some unique properties, name them.Solution 4

The unique properties shown by carbon are:

Tetravalency of carbon

Catenation

IsomerismQuestion 5

Explain the following:

(a) Tetravalency

(b) CatenationSolution 5

(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 6

Write any four properties of organic compounds that distinguish them from inorganic compounds.Solution 6

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 7

Why are organic compounds studied as a separate branch of chemistry?Solution 7

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 8

What are Hydrocarbons? Compare saturated and unsaturated hydrocarbons?Solution 8

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 9

Give reason for the existence of large numbers of organic compoundsSolution 9

Due to presence of unique properties of carbon like Tetravalency, catenation and Isomerism large number of organic compounds are formed.Question 10

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 CompoundSolution 10

(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 11

Name a compound of each type and draw the figure.

(a) Cyclic compound with single bond

(b) Cyclic compound with triple bondSolution 11

(a) Cyclic compound with single bond: cyclopentane

Structure:

(b) Cyclic compound with triple bond: cyclopentyne

Structure:

Question 12

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

(a) Saturated hydrocarbons

(b) Unsaturated hydrocarbonsSolution 12

The member of each of the following is:

(a) Saturated Hydrocarbon: Hexane (C6H14)

(b) Unsaturated Hydrocarbon: Hexene (C6H12)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.

Chapter 12 - Organic Chemistry Exercise Intext 2

Question 1

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

(a) Ketons

(b) Alcohols

(c) AldehydesSolution 1

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 2

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

a. Alkyne

b. AlcoholSolution 2

a. Butyne; its formula is C₄H₆.

b. Butanol; its formula is C₄H₉OH.Question 3

Which part of an organic compound determines

(i) Physical properties

(ii) Chemical propertiesSolution 3

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

(ii) Chemical properties: The functional group is responsible for the chemical properties.Question 4

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 4

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 5

(a) What is an alkyl group?

(b) Give the names of any three alkyl radicals. How are they formed?Solution 5

(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⁺

PropylQuestion 6

Give the names and the structural formula of the first three members of the homologous series of alkanesSolution 6

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

(i)

CH₄Methane

(ii)

C₂H₆Ethane

(iii)

C₃H₈PropaneQuestion 7

(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 7

(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 Exercise Ex. 12A

Question 1(a)

Write the IUPAC name of the following:

Solution 1(a)

2,2 dimethyl propaneQuestion 1(b)

Write the IUPAC name of the following:

Solution 1(b)

2-methyl butaneQuestion 1(c)

Write the IUPAC name of the following:

Solution 1(c)

PropeneQuestion 1(d)

Write the IUPAC name of the following:

Solution 1(d)

2,2-dimethyl pentaneQuestion 1(e)

Write the IUPAC name of the following:

CH₃ - C ≡ C - CH₂CH₃Solution 1(e)

3-PentyneQuestion 1(f)

Write the IUPAC name of the following:

Solution 1(f)

3-methyl but-1-yneQuestion 1(g)

Write the IUPAC name of the following:

Solution 1(g)

2,3-dimethyl pentaneQuestion 1(h)

Write the IUPAC name of the following:

Solution 1(h)

3-methyl heptaneQuestion 1(i)

Write the IUPAC name of the following:

Solution 1(i)

2-ButeneQuestion 1(j)

Write the IUPAC name of the following:

Solution 1(j)

Hept-2-yneQuestion 1(k)

Write the IUPAC name of the following:

Solution 1(k)

5,5-dimethyl hexan-1-alQuestion 1(l)

Write the IUPAC name of the following:

Solution 1(l)

Pentan-2-olQuestion 1(m)

Write the IUPAC name of the following:

Solution 1(m)

4-methyl pentan-1-oic acidQuestion 1(n)

Write the IUPAC name of the following:

Solution 1(n)

2-bromo-2-methyl butaneQuestion 1(o)

Write the IUPAC name of the following:

Solution 1(o)

1-bromo-3-methyl butaneQuestion 1(p)

Write the IUPAC name of the following:

Solution 1(p)

Prop-1-yneQuestion 1(q)

Solution 1(q)

MethanalQuestion 1(r)

Write the IUPAC name of the following:

CH₃-C≡C-HSolution 1(r)

1-propyneQuestion 1(s)

Solution 1(s)

PropanolQuestion 1(t)

Write the IUPAC name of the following:

Solution 1(t)

Ethanoic acidQuestion 1(v)

Write the IUPAC name of the following:

Solution 1(v)

1,2-dichloroethaneQuestion 2

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 C₄H₁₀OSolution 2

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-OHQuestion 3

Choose the correct answer:

(a) C₅H₁₁ is an

(i) Alkane

(ii) Alkene

(iii) Alkyne

(iv) Alkyl group

(b) A hydrocarbon of general formula C_nH_2n is

(i) C₁₅H₃₀

(ii) C₁₂H₂₆

(iii) C₈H₂₀

(iv) C₆H₁₄

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

(i) 5

(ii) 4

(iii) 3

(iv) 2

(d) CH₃-CH₂-OH and CH₃-O-CH₃ are

(i) Position isomer

(ii) Chain isomers

(iii) Homologous

(iv) Functional-group isomers

(e) The IUPAC name of compound is

(i) 3-trimethylhexane

(ii) 3-methyl hexane

(iii) 4-methyl hexaneSolution 3

1. (iv) CnH 2n + 1 is the formula for an alkyl group. Hence it is C₅H₁₁.
2. (i) A hydrocarbon of general CnH₂n is C₁₅H₃₀
   As the formula of Alkene is CnH₂n. Thus n + 2n = 72 3n = 72 n = 24. By filling value we get the molecular mass 72.
3. (iv) The total number of carbon chains that four carbon atoms form an alkane is 2.
4. (iv) Alcohol and ether are functional isomers as they have same molecular formula but different functional groups.
5. (ii) The IUPAC name of this compound is: 3-methyl hexane.

Question 4

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 4

(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 5

Define or explain chain isomerism and position isomerism with examples in each case.Solution 5

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 6

(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 6

(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-buteneQuestion 7

Which type of reaction will (i) ethane and (II) ethane undergo?Solution 7

(i) Ethane undergoes substitution reactions.

(ii) Ethene undergoes addition reactions.Question 8

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 8

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) MethoxymethaneQuestion 9

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 9

a. 

b. 

c. 

d. 

e. 

f. Question 10

Choosing only words from the following list, write down appropriate words to fill in the blanks from (a) to (e) given below. Addition, carbohydrates, C_nH_2n-2, C_nH_2n,C_nH_2n+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 10

The alkanes form an (a) electrochemical homologous series with the general formula (b) C_nH_2n+2. The alkanes are (c) saturated (d) hydrocarbons which generally undergo (e) substitution reactions.Question 11

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 bondSolution 11

 a.

 b.

 c.

Question 12

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 C_nH_2n.Solution 12

a. Ethanol

b. Ethanoic acid

c. EtheneQuestion 13

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

a. 

b. 

Solution 13

a. Propanal

b. PropanolQuestion 14

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 14

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 15(a)

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 15(a)

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 15(b)

The organic compound which undergoes substitution reaction is (v)……….(C₂H₂, C₂H₄, C₁₀H₁₈, C₂H₆)Solution 15(b)

The organic compound which undergoes substitution reaction is C₂H₆.Question 15(c)

(c) Draw the structural formulae of the two isomers of Butane. Give the correct IUPAC name of each of the isomer.Solution 15(c)

(c) Structural formulae of isomers ofButane are:

Butane2-methyl propaneQuestion 16

Name:

1. The saturated hydrocarbon containing two carbon atoms.
2. An alcohol with three carbon atom.
3. A triple bond hydrocarbon with two carbon atoms.

Solution 16

1. Ethane
2. Propanol
3. Ethyne 

Question 1(u)

Solution 1(u)

Ethanal 

Chapter 12 - Organic Chemistry Exercise 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 :

C_nH _2n+2Question 4

Draw the structures of isomers of

(a) Butane (b) Pentane

Write the IUPAC and common names of these isomersSolution 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 propaneQuestion 5

Write the

(a) Molecular formula

(b) Electron dot formula and

(c) Structural formula of methane and ethaneSolution 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 laboratorySolution 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+C₂H₆Question 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+HBrQuestion 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

HexachloroethaneQuestion 9

Name the compounds formed when methane burns in

(a) Sufficient air(b) insufficient air

Give a balanced equationSolution 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 + 4H₂OQuestion 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

C₂H₅B_r + Br₂ C₂H₄Br₂+HBr

Dibromoethane

C₂H₄Br₂ +Br₂ C₂H₃Br₃+HBr

Tribromoethane

C₂H₃Br₃ + Br₂ C₂H₂Br₄ + HBr

Tetrabromoethane

C₂H₂Br₄ +Br₂ C₂HBr₅ +HBr

Pentabromoethane

C₂HBr₅ +Br₂ C₂Br₆ + HBr

HexaBromoethaneQuestion 11

Name the compound prepared from

(a) Sodium propionate

(b) Methyl iodide

(c) Ethyl bromide

Write the balanced equation for the sameSolution 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+HBrQuestion 12

Write the equation for the complete combustion of

(i) methane (ii) ethane.Solution 12

(i) 

(ii) Question 13

Convert

(a) Methane into chloroform

(b) Sodium acetate into methane

(c) Methyl iodide into ethane

(d) Methane to methyl alcoholSolution 13

(a) Methane into chloroform

CH₄+Cl₂CH₃Cl+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) Methane to methyl alcohol

Question 14

Give three uses of:

(a) Methane

(b) ethaneSolution 14

(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 15

Under what conditions does ethane get converted to:

(a) Ethyl alcohol

(b) Acetaldehyde

(c) Acetic acidSolution 15

(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+H₂OQuestion 16

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 16

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 100^oC, ethane can be oxidized to ethanoic acid.

2C₂H₆ + 3O₂ 2CH₃COOH + 2H₂O

Chapter 12 - Organic Chemistry Exercise 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 C_nH_2n.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 C₄H_8.

(d) The molecular formula of alkene when there are 10 H atom in it C₅H_10.

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

(f) Lower homologus of alkene which contain four carbons is C₃H_6.

Higher homologus of alkene which contain four carbons is C₅H₁₀.Question 3(a)

Distinguish between the saturated hydrocarbon ethane and the unsaturated hydrocarbon ethene by drawing their structural formulae.Solution 3(a)

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 3(b)

Draw the structure of isomers of butane and write their IUPAC names.Solution 3(b)

There are two isomers are possible for butane:

Question 4

Give a balanced equation for the lab. Preparation of ethylene. How is the gas collected?Solution 4

Balanced Equation of ethylene:

CH₃-CH₂OH + H₂SO₄ CH₃-CH₂HSO₄+H₂O

CH₃-CH₂HSO₄CH₂=CH₂

The gas is collected by downward displacement of water.Question 5

How is ethene prepared by:

(a) Dehydrohalogenation reaction?

(b) Dehydration reaction?

Give equations and name the products formed.Solution 5

(a) Dehydrohalogenation reaction:

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

Ethene

(b) Dehydration reaction:

C₂H₅OH C₂H₄+H₂O

EtheneQuestion 6(a)

Ethylene when reacts with halogens (chlorine and bromine) form saturated products. Name them and write balanced equations.Solution 6(a)

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 ethaneQuestion 6(b)

Give the conditions and the main product formed by hydrogenation of ethylene.Solution 6(b)

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

C₂H₄ +H₂ C₂H₆Question 7

Convert ethanol into ethene using

(a) Solid dehydrating agent

(b) Hot conc. H₂SO₄

Give only balanced equations.Solution 7

Conversion of ethanol to ethene by using

(a) Solid dehydrating agent:

(b) Hot conc. H₂SO₄:

Question 8

Write the following properties of ethene:

(a) Physical state

(b) Odour

(c) Density as compared to air

(d) SolubilitySolution 8

(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 9

How would you convert:

(a) Ethene into 1,2-dibromoethane

(b) Ethene into ethyl bromideSolution 9

(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 bromideQuestion 10

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 10

(a) C₂H₄+3O₂ 2CO₂ +2H₂O + heat

(b) CH₂=CH₂+Cl₂ CH₂(Cl)-CH₂(Cl)

(c) CH₂=CH₂ + HCl CH₃-CH₂-Cl

(d) C₂H₄ +H₂ C₂H₆Question 11

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

(a) CH₄ABCD

(b) C₂H₂ABCD

(c) C₂H₄ +B C₂H₆Solution 11

(a) CH₄CH₃ClCH₂Cl₂CHCl₃CCl₄

A= monochloromethane

B= dichloromethane

C=Trichloromethane

D=Tetrachloromethane

(b) C₂H₂C₂H₄C₂H₆C₂H₅BrC₂H₄Br

A= Ethene

B=ethane

C=bromoethane

D=dibromoethane

(c) C₂H₄ +H₂C₂H₆

B= hydrogenQuestion 12

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 12

(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

chloroethaneQuestion 13

What do you observe when ethylene is passed through alkaline KMnO₄ solution?Solution 13

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 solutionQuestion 14

Name three compounds formed by ethylene and give the use of these compounds.Solution 14

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 Exercise 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:

C_nH_2n-2Question 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-yneQuestion 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, C₃H₆Solution 6

The following compounds can be classified as:

C₃H₄:- Alkynes

C₃H₈:- Alkanes

C₅H₈:- Alkynes

C₃H₆:- AlkenesQuestion 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 conversions.

1. An alkene to an alkane
2. An alkene to an alcohol.
3. An alkyne to an alkene.

Solution 9

1. CH₂ =CH₂  + H₂  CH₃ -CH₃
2. CH₂ =CH₂  + H₂O ⟶ CH₃ -CH₂-OH
3. CH ≡CH + H₂  CH₂ =CH₂  

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) 
Question 11

Substitution reactions are characteristic reactions of ………….. (alkynes/alkenes/alkanes).Solution 11

Substitution reactions are characteristic reactions of alkanes.Question 12

(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 waterSolution 12

  (a)  i. 

ii. 

(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 +H₂OC₂H₅OHQuestion 13

Give reasons:

(a) Ethyne is more reactive than ethene.

(b) Ethene is more reactive then ethane.

(c) Hydrocarbons are excellent fuels.Solution 13

(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 + 2H₂OQuestion 14

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 acetateSolution 14

a. 

i. 

ii. 

b. 

i.   

ii. 

iii. 

iv. 

Question 15

(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 15

(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.

Chapter 12 - Organic Chemistry Exercise Ex. 12E

Question 1

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, CH₄Solution 1

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

b. ii. Ethanol.

c. C₅H₁₀ is an alkene, while the rest are alkanes.Question 2

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.Solution 2

i. 

ii. 

iii. 

iv. Question 3

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 etheneSolution 3

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°CQuestion 4

i. Define isomerism.

ii. Give the IUPAC name of the isomer C4H10 which has a branched chain.Solution 4

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 propaneQuestion 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 CH₃CHOQuestion 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 dichromateSolution 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) C₂H₅OHSolution 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 the organic compound which is:

1. Used for illuminating country houses
2. Used for making a household plastic material
3. Called 'wood spirit'
4. Poisonous and contain OH group
5. Consumed as a drink
6. Made from water gas
7. Solvent for gums and resins
8. Dehydrated to produce ethene

Solution 12

1. Used for illuminating country houses : Ethyne
2. Used for making a household plastic material: ethyne
3. Called 'wood spirit' : Methanol
4. Poisonous: Methanol
5. Consumed as a drink: Ethanol
6. Made from water gas: Methanol
7. Ethanol
8. Ethyl alcohol

Question 13

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 13

(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 14

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 IodoethaneSolution 14

(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 + NaIQuestion 15

(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 15

(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 +C₂H₂Question 16

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 hydroxideSolution 16

(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

Chapter 12 - Organic Chemistry Exercise 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: C_nH_2n+1COOHQuestion 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 acidSolution 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

EthanalQuestion 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 acidQuestion 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  + H₂O  CH₃CHO

CH₃CHO + O₂  2CH₃COOH
Question 7

What do you notice when acetic acid reacts with

(a) Litmus

(b) Metals

(c) Alkalies

(d) alcoholSolution 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 + H₂OQuestion 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 bicarbonateSolution 8

(a) 2CH₃COOH + Zn (CH₃COO)₂Zn + H₂

(b) CH₃COOH + NaOH CH₃COONa + H₂O

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

(d) CH₃COOH + NaHCO₃ CH₃COONa + H₂O +CO₂Question 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 solutionSolution 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 anhydrideSolution 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 Exercise Misc. Ex.

Question 5

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 5

(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 2010

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 2010

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°CQuestion 2011

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 2011

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 2012

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 2012

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 2013

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-propanolSolution 2013

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 2014

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 2014

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 + NaClQuestion 2015

(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 hydroxideSolution 2015

(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