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NCERT Solutions For Class 12 Chemistry chapter 15-Polymers

NCERT Solutions for Class 12 Chemistry

NCERT Solutions for class-12 Chemistry Chapter 15 Polymers is prepared by our senior and renown teachers of Physics Wallah primary focus while solving these questions of class-12 in NCERT textbook, also do read theory of this Chapter 15 Polymers while going before solving the NCERT questions. Our Physics Wallah team Prepared Other Subjects NCERT Solutions for class 12.

Chapter 15 Polymers

Answer the following Questions.

Question1. Explain the terms polymer and monomer.

Solution :
Polymers are high molecular mass macromolecules composed of repeating structural units derived from monomers. Polymers have a high molecular mass (103 − 107 u). In a polymer, various monomer units are joined by strong covalent bonds. Polymers can be natural as well as synthetic. Polythene, rubber, and nylon 6, 6 are examples of polymers.

Monomers are simple, reactive molecules that combine with each other in large numbers through covalent bonds to give rise to polymers. For example, ethene, propene, styrene, vinyl chloride.

Question2. What are natural and synthetic polymers? Give two examples of each type.

Solution :
Natural polymers are polymers that are found in nature. They are formed by plants and animals. Examples include protein, cellulose, starch, etc.

Synthetic polymers are polymers made by human beings. Examples include plastic (polythene), synthetic fibres (nylon 6, 6), synthetic rubbers (Buna − S).

Question3. Distinguish between the terms homopolymer and copolymer and give an example of each.

Solution :

Homopolymer 

Copolymer 

The polymers that are formed by the polymerization of a single monomer are known as homopolymers. In other words, the repeating units of homopolymers are derived only from one monomer. For example, polythene is a homopolymer of ethene.

The polymers whose repeating units are derived from two types of monomers are known as copolymers. For example, Buna−S is a copolymer of 1, 3-butadiene and styrene.

Question4. How do you explain the functionality of a monomer?

Solution :
The functionality of a monomer is the number of binding sites that is/are present in that monomer. 

For example, the functionality of monomers such as ethene and propene is one and that of 1, 3-butadiene and adipic acid is two.

Question5. Define the term polymerisation.

Solution :
Polymerization is the process of forming high molecular mass (103 − 107 u) macromolecules, which consist of repeating structural units derived from monomers. In a polymer, various monomer units are joined by strong covalent bonds. 

Question6. Is NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers, a homopolymer or copolymer?

Solution :
NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers is a homopolymer because it is obtained from a single monomer unit, NH2−CHR−COOH.

Question7. In which classes, the polymers are classified on the basis of molecular forces?

Solution :
On the basis of magnitude of intermolecular forces present in polymers, they are classified into the following groups:

(i) Elastomers

(ii) Fibres

(iii) Thermoplastic polymers

(iv) Thermosetting polymers

Question8. How can you differentiate between addition and condensation polymerisation?

Solution :
Addition polymerization is the process of repeated addition of monomers, possessing double or triple bonds to form polymers. For example, polythene is formed by addition polymerization of ethene. 

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Condensation polymerization is the process of formation of polymers by repeated condensation reactions between two different bi-functional or tri-functional monomers. A small molecule such as water or hydrochloric acid is eliminated in each condensation. For example, nylon 6, 6 is formed by condensation polymerization of hexamethylenediamine and adipic acid.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question9. Explain the term copolymerisation and give two examples.

Solution :
The process of forming polymers from two or more different monomeric units is called copolymerization. Multiple units of each monomer are present in a copolymer. The process of forming polymer Buna−S from 1, 3-butadiene and styrene is an example of copolymerization

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Nylon 6, 6 is also a copolymer formed by hexamethylenediamine and adipic acid.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question10. Write the free radical mechanism for the polymerisation of ethene.

Solution :
Polymerization of ethene to polythene consists of heating or exposing to light a mixture of ethene with a small amount of benzoyl peroxide as the initiator.

The reaction involved in this process is given below:

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question11. Define thermoplastics and thermosetting polymers with two examples of each.

Solution :
Thermoplastic polymers are linear (slightly branched) long chain polymers, which can be repeatedly softened and hardened on heating. Hence, they can be modified again and again. Examples include polythene, polystyrene.

Thermosetting polymers are cross-linked or heavily branched polymers which get hardened during the molding process. These plastics cannot be softened again on heating. Examples of thermosetting plastics include bakelite, urea-formaldehyde resins. 

Question12. Write the monomers used for getting the following polymers.

(i) Polyvinyl chloride (ii) Teflon (iii) Bakelite

Solution :
(i) Vinyl chloride (CH2=CHCl)

(ii) Tetrafluoroethylene (CF2 = CF2)

(iii) Formaldehyde (HCHO) and phenol (C6H5OH)

Question13. Write the name and structure of one of the common initiators used in free radical addition polymerisation.

Solution :
One common initiator used in free radical addition polymerization is benzoyl peroxide. Its structure is given below.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question14. How does the presence of double bonds in rubber molecules influence their structure and reactivity?

Solution :
Natural rubber is a linear cis-polyisoprene in which the double bonds are present between C2 and C3 of the isoprene units.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Because of this cis-configuration, intermolecular interactions between the various strands of isoprene are quite weak. As a result, various strands in natural rubber are arranged randomly. Hence, it shows elasticity.

Question15. Discuss the main purpose of vulcanisation of rubber.

Solution :
Natural rubber though useful has some problems associated with its use. These limitations are discussed below:

  •  Natural rubber is quite soft and sticky at room temperature. At elevated temperatures (> 335 K), it becomes even softer. At low temperatures (< 283 K), it becomes brittle. Thus, to maintain its elasticity, natural rubber is generally used in the temperature range of 283 K-335 K.
  •  It has the capacity to absorb large amounts of water.
  • It has low tensile strength and low resistance to abrasion.
  •  It is soluble in non-polar solvents.
  • It is easily attacked by oxidizing agents.

Vulcanization of natural rubber is done to improve upon all these properties. In this process, a mixture of raw rubber with sulphur and appropriate additive is heated at a temperature range between 373 K and 415 K. 

Question16. What are the monomeric repeating units of Nylon-6 and Nylon-6, 6?

Solution :
The monomeric repeating unit of nylon 6 isNCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers, which is derived from Caprolactam.

The monomeric repeating unit of nylon 6, 6 isNCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers, which is derived from hexamethylene diamine and adipic acid.

Question17. Write the names and structures of the monomers of the following polymers:

(i) Buna-S (ii) Buna-N

(iii) Dacron (iv) Neoprene

Solution :

Polymer 

Monomer 

Structure of monomer 

i

Buna-S

1, 3-butadiene 

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Styrene

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

ii

Buna-N

1, 3-butadiene 

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Acrylonitrile

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

iii

Neoprene 

Chloroprene

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

iv

Dacron

Ethylene glycol 

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Terephthalic acid

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question18. Identify the monomer in the following polymeric structures.

(i)

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

(ii) 

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Solution :
(i) The monomers of the given polymeric structure are decanoic acid NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymersand hexamethylene diamine m58a4eac6.gif.

(ii) The monomers of the given polymeric structure are 

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question19. How is dacron obtained from ethylene glycol and terephthalic acid?

Solution :
The condensation polymerisation of ethylene glycol and terephthalic acid leads to the formation of dacron.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question20. What is a biodegradable polymer? Give an example of a biodegradable aliphatic polyester.

Solution :
A polymer that can be decomposed by bacteria is called a biodegradable polymer.

Poly-β-hydroxybutyrate-CO-β- hydroxyvalerate (PHBV) is a biodegradable aliphatic polyester.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question21. What are polymers?

Solution :
Polymers are high molecular mass macromolecules, which consist of repeating structural units derived from monomers. Polymers have a high molecular mass (103 − 107 u). In a polymer, various monomer units are joined by strong covalent bonds. These polymers can be natural as well as synthetic. Polythene, rubber, and nylon 6, 6 are examples of polymers.

Question22. How are polymers classified on the basis of structure?

Solution :
Polymers are classified on the basis of structure as follows:

1. Linear polymers:

These polymers are formed of long straight chains. They can be depicted as:

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

For e.g., high density polythene (HDP), polyvinyl chloride, etc.

2. Branched chain polymers:

These polymers are basically linear chain polymers with some branches. These polymers are represented as:

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

For e.g., low density polythene (LDP), amylopectin, etc.

3. Cross-linked or Network polymers:

These polymers have many cross-linking bonds that give rise to a network-like structure. These polymers contain bi-functional and tri-functional monomers and strong covalent bonds between various linear polymer chains. Examples of such polymers include bakelite and melmac.

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question23. Classify the following as addition and condensation polymers: Terylene, Bakelite, Polyvinyl chloride, Polythene.

Solution :
Addition polymers:

Polyvinyl chloride, polythene 

Condensation polymers:

Terylene, bakelite 

3. Write the names of monomers of the following polymers:

(i) Bakelite

(ii) Nylone-6,6

(iii) Polythene

Solution :
(i)  _5b84e991.gif

(ii) Nylon-6,6 is a polymer formed by the polymerization reaction of hexamethylenediamine and adipic acid.
Thus, the monomers of nylon-6,6 are of hexamethylenediamine and adipic acid.
The structures of of hexamethylenediamine and adipic acid are as follows:

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

(iii) Polythene is a polymer formed by the polymerization reaction of ethylene molecules.
Thus, the monomer of polythene is ethylene.
The structure of ethylene is as follows:

NCERT Solutions for Class 12  Chemistry Chapter 15 - Polymers

Question24. Classify the following as addition and condensation polymers: Terylene, Bakelite, Polyvinyl chloride, Polythene.

Solution :
Addition polymers:

Polyvinyl chloride, polythene 

Condensation polymers:

Terylene, bakelite 

Question25. Explain the difference between Buna-N and Buna-S.

Solution :
Buna − N is a copolymer of 1, 3−butadiene and acrylonitrile. 

Buna − S is a copolymer of 1, 3−butadiene and styrene.

Question26. Arrange the following polymers in increasing order of their intermolecular forces.

(i) Nylon 6, 6, Buna-S, Polythene.

(ii) Nylon 6, Neoprene, Polyvinyl chloride.

Solution :
Different types of polymers have different intermolecular forces of attraction. Elastomers or rubbers have the weakest while fibres have the strongest intermolecular forces of attraction. Plastics have intermediate intermolecular forces of attraction. Hence, the increasing order of the intermolecular forces of the given polymers is as follows:

(i) Buna − S < polythene < Nylon 6, 6

(ii) Neoprene < polyvinyl chloride < Nylon 6

NCERT Solutions For Class 12 Chemistry Chapter Wise.

  1. Chapter 1 The Solid States

  2. Chapter 2 Solutions

  3. Chapter 3 Electrochemistry

  4. Chapter 4 Chemical Kinetics

  5. Chapter 5 Surface Chemistry

  6. Chapter 6 General Priciples and Processes of Isolation of Elements

  7. Chapter 7 The P Block Elements

  8. Chapter 8 The D and F Elements

  9. Chapter 9 Coordination Compounds

  10. Chapter 10 Haloalkanes and Haloarenes

  11. Chapter 11 Alcohols, Phenols and Ethers

  12. Chapter 12 Aldehydes, ketones and Carboxylics Acids

  13. Chapter 13 Amines

  14. Chapter 14 Biomolecules

  15. Chapter 15 Polymers

  16. Chapter 16 Chemistry In Everyday Life

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