Q: Define the term polymerisation.

(NH−CHR−CO)n is a homopolymer as it is obtained from a single monomer unit, NH2−CHR−COOH. Note: Homopolymers are formed by the polymerisation of a single monomer. The repeating units of homopolymers are derived only from one monomer.In copolymers, the repeating units are derived from two types of monomers.

Question 1

The biodegradable polymer is:

Accepted Answer

Nylon-2-Nylon 6

Question 2

Regarding cross-linked or network polymers, which of the following statements is incorrect?

Accepted Answer

Cross linked or network polymers are formed from bi-functional and tri-functional monomers and contain strong covalent bonds between various linear polymer chains, e.g. bakelite, melamine etc. Option (4) is not related to cross-linkingSo option (4) should be the correct option.

Question 3

D(+)  glucose reacts with hydroxylamine and yields an oxime. The structure of the oxime would be:

Accepted Answer

Glucose reacts with hydroxyl amine to from an oxime.

Question 4

Which one of the following is an example of a thermosetting polymer?

Accepted Answer

Thermosetting polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become in fusible. Most common examples are bakelite.

Question 5

Which of the following organic compounds polymerizes to form the polyester Dacron?

Accepted Answer

Dacron or terylene is the best known example of polyesters. It is manufactured by heating a mixture of ethylene glycol and terephthalic acid at 420 to460 K  in the presence of zinc acetate-antimaony, trioxide catalyst.

Question 6

Nylon is an example of:

Accepted Answer

Nylon is polyamide.

Question 7

Explain the terms polymer and monomer.

Accepted Answer

Polymer Polymer is a high molecular mass macro-molecule consisting of repeating structural units derived from monomers. The molar mass of polymer is around 103−107u. There are strong covalent bonds which joints various monomer units in a polymer.Examples of polymers include Rubber, polythene, Teflon and nylon 6.MonomerMonomer is a simple molecule capable of undergoing polymerization and leading to the formation of the corresponding polymer. Monomers are reactive molecules that combine with each other in large numbers through covalent bonds to form polymers. Examples of monomers include ethene, propene, styrene and vinyl chloride.In the given reaction Adipic acid and hexamethylenediamine are monomers and nylon 6,6 is a polymer.

Question 8

What are natural and synthetic polymers? Give two examples of each type.

Accepted Answer

Natural polymersNatural polymers are high molecular mass macromolecules and are found in nature (plants and animals). They are formed by plants and animals.The examples are proteins, nucleic acids, cellulose, starch etc.Synthetic polymersSynthetic polymers are man-made high molecular mass macromolecules. These include synthetic plastics, fibres and rubbers. The two specific examples are polythene and dacron.

Question 9

Distinguish between the terms homopolymer and copolymer and give an example of each.

Accepted Answer

Homopolymers are formed by the polymerisation of a single monomer. The repeating units of homopolymers are derived only from one monomer. Examples includes polythene which is a homopolymer of ethene.In copolymers, the repeating units are derived from two types of monomers. Example includes Buna -S, which is a copolymer of 1,3 Butadiene and styrene.

Question 10

How do you explain the functionality of a monomer?

Accepted Answer

Functionality of a monomer is the number of bonding sites present in the monomer.For example, the monomers ethene and propene have the functionality of 1 each.The monomers 1,3-butadiene and adipic acid have the functionality of 2 each.

Question 11

Define the term polymerisation.

Accepted Answer

(NH−CHR−CO)n​ is a homopolymer as it is obtained from a single monomer unit,  NH2​−CHR−COOH. Note: Homopolymers are formed by the polymerisation of a single monomer. The repeating units of homopolymers are derived only from one monomer.In copolymers, the repeating units are derived from two types of monomers.

Question 12

Is(NH−CHR−CO)n , a homopolymer or copolymer?

Accepted Answer

It is a homopolymer because the repeating structural unit has only one type of monomer, i.e., NH2​ -CHR-COOH.

Question 13

Why do elastomers possess elastic properties?

Accepted Answer

In elastomers, the polymeric chains are held by weak intermolecular forces of attraction. These weak binding forces allow them to stretch and a few cross-links are there in between the chains, which helps them to retract after stretching or releasing forces. Due to this elastomers are elastic in nature.

Question 14

How can you differentiate between addition and condensation polymerisation?

Accepted Answer

In addition polymerization, the molecules of the same or different monomers add together to form a large polymer molecule. Condensation polymerization is a process in which two or more bi-functional molecules undergo a series of condensation reactions with the elimination of some simple molecules and leading to the formation of polymers. For example, ethylene is converted into polyethene by addition polymerization and Nylon-6 is prepared from hexamethylene diamine and adipic acid by condensation polymerization.

Question 15

Explain the term copolymerisation and give two examples.

Accepted Answer

Copolymerisation is a process in which a mixture of more than one monomeric species is allowed to polymerise. The copolymer contains multiple units of each monomer in the chain. The examples are copolymers of 1,3-butadiene and styrene, hexamethylene diamine and adipic acid (Nylon-6,6) and 1,3-butadiene and acrylonitrile.

Question 16

Write the free radical mechanism for the polymerisation of ethene.

Accepted Answer

In the chain initiation step, the decomposition of benzoyl peroxide gives benzoyl free radical which further gives phenyl free radical.Phenyl free radical adds to C=C double bond of ethene and generates a new free radical.In chain propagating step, the newly generated free radical adds to another ethene molecule to form larger free radical. This process repeats several times.In the chain termination step, two free radicals combine to form polyethene.

Question 17

Define thermoplastics and thermosetting polymers with two examples of each.

Accepted Answer

A thermoplastic polymer can be repeatedly softened on heating and hardened on cooling. Hence, it can be used again and again. The examples are polythene, polypropylene, etc. A thermosetting polymer is a permanent setting polymer as it gets hardened and sets during moulding process and cannot be softened again. The examples are bakelite and melamine-formaldehyde polymers.

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Solution for Class 12, Chemistry, Polymers

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