2nd PUC Chemistry Question Bank Chapter 15 Polymers

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Karnataka 2nd PUC Chemistry Question Bank Chapter 15 Polymers

2nd PUC Chemistry Polymers NCERT Textbook Questions

Question 1.
Explain the terms polymer and monomer.
Answer:
Polymers are high molecular mass of macromolecules composed of repeating structural units derived from monomers. Polymers have a high molecular mass (103-107u). 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.

Question 2.
What are natural and synthetic polymers? Give two examples of each type.
Answer:
Natural polymers:
Natural polymers are high molecular mass macromolecules and are found in nature mainly in plants and animals. For example, protein, nucleic acids, starch, cellulose, etc.

Synthetic polymer:
Synthetic polymers are man-made high molecular mass macromolecules. For example, plastics (Polyethene, P.V.C.), synthetic fibers (Polyesters, Nylon-6,6), synthetic rubber (Neoprene, Buna-S), etc.

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Question 3.
Distinguish between the terms homopolymer and copolymer and give an example of each.
Answer:

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

Question 4.
How do you explain the functionality of a monomer?
Answer:
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.

Question 5.
Define the term polymerisation.
Answer:
Polymerization is the process of formation of a high molecular mass polymer from one or more types of monomers. Polymerization leads to the linkage together of several repeating structural units with covalent bonds.

Question 6.
Is ( NH-CHR-CO )8, a homopolymer or copolymer?
Answer:
(NH CHR-CO)8 is a homopolymer because it is obtained from a single monomer unit, NH2-CHR-COOH.

Question 7.
In which classes, the polymers are classified on the basis of molecular forces?
Answer:
On the basis of molecular forces present between the chains of various polymers, these are classified as:

  • Elastomers
  • Fibres
  • Thermoplastics
  • Thermo setting plastics.

Question 8.
How can you differentiate between addition and condensation polymerisation?
Answer:
Addition polymerisation is the process of repeated addition of monomers, possessing double or triple bonds to form polymers. For example, polythene is formed by additional polymerization of ethene

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 1
Condensation polymerization is the process Of the 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 polymerisation of hexamethylene diamine and adipic acid.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 2

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Question 9.
Explain the term copolymerization and give two examples.
Answer:
The formation of 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 BunaS from 1, 3-butadiene, and styrene is an example of copolymerization.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 3
Nylon 6,6 is also a copolymer formed by hexamethylene diamine and adipic acid.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 4

Question 10.
Write the free radical mechanism for the polymerisation of ethene.
Answer:
Polymerization of ethene to polythene consists of heating or exposing to a light mixture of ethene with a small amount of benzoyl peroxide as the initiator. The reaction involved in this process is given below:
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 5
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 6

Question 11.
Define thermoplastics and thermosetting polymers with two examples of each.
Answer:
Thermoplastics are polymers which can be easily softened repeatedly on heating and hardened on cooling. Therefore, it can be used again and again. For example, polyethylene and polyvinyl chloride. Thermosetting polymers are those which undergo permanent change on heating. They become hard and infusible on heating and cannot be softened again. For example, Bakelite, and Melamine formaldehyde.

Question 12.
Write the monomers used for getting the following polymers.

  1. Polyvinyl chloride
  2. Teflon
  3. Bakelite

Answer:

  1. Vinyl chloride (CH2 = CHCI)
  2. Tetrafluro ethylene (CF2 = CF2)
  3. Formaldehyde (HCHO) and phenol (C6H5OH)

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Question 13.
Write the name and structure of one of the common initiators used in free radical addition polymerisation.
Answer:
One common initiator used in tree radical addition polymerization is benzoyl peroxide. Its structure is given below.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 7

Question 14.
How does the presence of double bonds in rubber molecules influence their structure and reactivity?
Answer:
Natural rubber is a linear cis-polyisoprene in which the double bonds are present C2 and C3 of the isoprene units.
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 8
Because of this cis — configuration, intermolecular interactions between the various standard of isoprene are quite weak. As a result, various strands in natural rubber are arranged randomly. Hence it shows elasticity.

Question 15.
Discuss the main purpose of vulcanisation of rubber.
Answer:
The main purpose of vulcanization of rubber is to improve the following draw-back of natural rubber:

  • At high temperature (T >335K) natural rubber becomes soft.
  • At low temperature (T< 283K) natural rubber becomes brittle.
  • Natural rubber is soluble in non-polar solvents.
  • It is non-resistant to attack by oxidizing agents.

Question 16.
What are the monomeric repeating units of Nylon-6 and Nylon-6,6?
Answer:
The monomeric repeating unit of nylon 6 is [NH – (CH2)5 – CO], which is derived from caprolactam.
The monomeric repeating unit of nylon 6, 6 is [NH – (CH2)6 – NH – CO – (CH2)4 – CO], which is derived from hexamethylene diamine and adipic acid.

Question 17.
Write the names and structures of the monomers of the following polymers:
(i) Buna-S
(ii) Buna-N
(iii) Dacron
(iv) Neoprene
Answer:
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 9

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Question 18.
Identify the monomer in the following polymeric structures.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 10
Answer:
Monomers are:

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 11

Question 19.
How is dacron obtained from ethylene glycol and terephthalic acid?
Answer:
The condensation polymerisation of ethylene glycol and terephthalic acid leads to the formation of dacron.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 12

Question 20.
What is a biodegradable polymer? Give an example of a biodegradable aliphatic polyester.
Answer:
A polymer that can be decomposed by bacteria is called a biodegradable polymer. Poly – β- hydroxybutyrate – Co -β – hydroxy valerate (PHBV) is a biodegradable aliphatic polyester.

2nd PUC Chemistry Question Bank Chapter 15 Polymers - 13

2nd PUC Polymers Additional Questions

Question 1.
How are polymers classified on the basis of the solution?
Answer:

  • Linear polymers such as high-density polythene (HDP), Polyvinylchloride, nylons, polyester etc.
  • Branched polymers such as low-density polythene (LDP), amylopectin, glycogen etc.

Question 2.
What is the difference between Buna-S and Buna-N?
Answer:
Both are copolymers basically Buna-N is a copolymer of
1,3- butadiene and acrylonitrile. Buna-S is a copolymer of
1,3- butadiene and styrene.

Question 3.
What are the monomeric units of Nylon 6 and Nylon 6, 6?
Answer:
The monomeric repeating unit of Nylon 6 :
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 14
which is derived from caprolactam monomeric repeating unit of Nylon 6,6:
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 15
which is derived from 2 monomers, hexamethylenediamine, and adipic acid, and has the following structure.

Question 4.
What are the disadvantages of natural rubber which are compromised by vulcanisation?
Answer:

  • It becomes more soft and sticky at high temperatures and brittle at low temperatures.
  • It. has a large water absorption capacity and low tensile strength and low resistance to abrasion.
  • Not resistant to the action of organic solvents.
  • Easily attacked by oxygen and other oxidising agents.

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Question 5.
What does PMMA stand for?
Answer:
Poly(methyl methacrylate)

Question 6.
How are polymers classified on the basis of molecular forces?
Answer:

  • Elastomers
  • Fibres
  • Thermoplastic
  • Thermosetting.

Question 7.
What is copolymerisation (and give an example)?
Answer:
When 2 or more different monomers are allowed to polymerise together, the product is called a copolymer and the process is called copolymerisation.
Ex: Buna-S: 1, 3 – butadiene and styrene.

Question 8.
What thermoplastic and thermosetting polymers?
Answer:
Thermoplastics are linear polymers which can be repeatedly softened on heating and hardened on cooling and hence can.be repeatedly used.
ex: polythene, polypropene etc.

Thermosetting polymers are on the other hand permanently setting polymers. On heating, they harden and cant be softened again.
ex: bakelite, urea-formaldehyde resin.

Question 9.
What is the functionality of a polymer?
Answer:
It is the number of binding sites in a molecule.
The functionality of styrene is one, whereas it is for adipic acid.

Question 10.
Write a free radical mechanism for polymerisation of ethene.
Answer:
Initiation:
2nd PUC Chemistry Question Bank Chapter 15 Polymers - 16

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