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Q1. Give an example of synthetic rubber and how it is obtained?

Solution

Synthetic rubber i.e. gutta percha is obtained by the free radical polymerization of isoprene and has all trans-configuration.

Q2. Given one example each of: (i) addition polymers, (ii) condensation polymers, (iii) copolymers

Solution

Type of polymer Example Structure (i) Addition polymers Polyethene or Polythene (ii) Condensation polymers Nylon 6,6 (iii) Copolymer Buna-S    

Q3. Polymers that are found in nature are called:

• 1) Homopolymers
• 2) Addition polymer
• 3) Synthetic polymer
• 4) Natural polymers

Solution

Polymers which are found in nature i.e animals and plants are called natural polymers. For example: starch, cellulose, proteins, nucleic acids, natural rubber etc.  

Q4. Write the structures of monomers used in the preparation of: (a) Teflon (b) PMMA Or (a) How does vulcanization change the character of natural rubber? (b) Why are the numbers 6,6 and 6 put in the names of nylon-6,6 and nylon-6 respectively?

Solution

(a) Tetrafluoroethylene: CF₂ = CF₂ (b) Methyl methacrylate Or (a) Heating rubber with sulphur causes cross-linking of polymer chains through disulphide bonds. This makes rubber hard and stiff. It prevents the intermolecular movement of rubber springs resulting in the change of physical character of rubber. (b) Nylon-6 is obtained from the monomer caprolactum which contains 6 carbon atoms. Nylon-6,6 is a condensation polymer of hexamethylene diamine and adipic acid. The two monomers have 6 carbon atoms each.

Q5. Condensation polymer differs from addition polymers:

• 1) Molecular formula of the repeating structural unit can be same or different as that of the starting monomer
• 2) Molecular formula of the repeating structural unit is generally different as that of the starting monomer
• 3) Molecular formula of the repeating structural unit is the same as that of the starting monomer
• 4) Formation of water as the bi-product

Solution

Condensation polymer differs from addition polymers with molecular formula of the repeating structural unit is generally different as that of the starting monomer.

Q6. Buna-S is a copolymer of:

• 1) Chloroprene and Butadiene
• 2) Butadiene and styrene
• 3) Urea and styrene
• 4) Adipic acid and hexamethylenediamine

Solution

Buna-S is a copolymer of butadiene and styrene. It is prepared by co-polymerization of 1,3 butadiene and styrene along with sodium.

Q7. Isoprene is the monomer of:

• 1) Teflon
• 2) Natural rubber
• 3) Bakelite
• 4) PVC

Solution

Isoprene is the monomer of Natural Rubber. Natural rubber may be considered as a linear polymer of isoprene (2-methyl-1, 3-butadiene) and is also called as cis-1,4-polyisoprene.

Q8. Differentiate between molecular structures and behaviour of thermoplastic and thermosetting polymers. Give one example of each type.

Solution

Property Thermoplastic polymers Thermosetting polymers Molecular Structure Linear or slightly branched long chain molecules. Cross linked or heavily branched molecules. Behaviour Can undergo softening on heating and hardening on cooling. Do not soften on heating.   They can be reused. They cannot be reused. Example Some commonthermoplastics are polythene, polystyrene, polyvinyls, etc. Some commonexamples are bakelite, urea-formaldelyde resins, etc.  

Q9. What is PVC and how is it prepared?

Solution

PVC i.e, polyvinyl chloride is a synthetic polymer. Vinyl chloride polymerises in the presence of peroxides to give PVC.

Q10. Nylon-6,6 is obtained by the process of:

• 1) Synthetic polymerization
• 2) Addition polymerization
• 3) Condensation polymerization
• 4) Natural rubber

Solution

Hexamethylenediamine reacts with adipic acid to give Nylon-6,6 i.e a condensation polymer formed by the joining of the monomer units with loss of water molecule.

Q11. What are the uses of Bakelite?

Solution

Bakelite is used as a binding glue for laminated wooden planks, and in varnishes and lacquers. Also used in the manufacture of combs, fountain pens, electrical goods, gramophone records etc.

Q12. What is PMMA, PAN and PVC?

Solution

PMMA is polymethylmethacrylate. PAN stands for Polyacrylonitrile and PVC is Polyvinylchloride.

Q13. Give examples of synthetic rubber?

Solution

Examples of synthetic rubber are neoprene and Buna-S.

Q14. Distinguish between the terms homopolymer and copolymer and give an example of each.

Solution

The addition polymers formed by the polymerisation of a single monomeric species are known as homopolymers, e.g., polythene.   The polymers made by addition polymerisation from two different monomers are termed as copolymers, e.g., Buna-S, Buna-N, etc.

Q15. How is nylon-6,6 prepared?

Solution

Nylon-6,6 is prepared by the method of condensation polymerisation process. Hexamethylenediamine combines with adipic acid to give the macromolecule Nylon-6,6 with the elimination of water molecule.  

Q16. How is polyethylene prepared?

Solution

Polyethylene is prepared by heating ethylene to 473K under a pressure of 1500 atm. This polymerisation occurs as free radical mechanism which is initiated by oxygen.

Q17. Condensation polymerisation of ethylene glycol and terepthalic acid gives:

• 1) Buna-S
• 2) Terylene
• 3) Glyptal
• 4) PVC

Solution

Condensation polymerisation of ethylene glycol and terepthalic acid gives Terelyne with elimination of water. The reaction is carried out at 425-475K.

Q18. What is a copolymerisation reaction? Give example.

Solution

The polymers made by addition polymerisation from two different monomers are termed as copolymers. A mixture of two unsaturated monomers exhibits copolymerisation and forms a co-polymer containing multiple units of each monomer. e.g., Buna-S, Buna-N, etc.

Q19. How natural polymers differ from synthetic polymer?

Solution

Polymers that are found in nature i.e., animals and plants are called natural polymers. For example, starch, cellulose, proteins, natural rubber. Polymers that are man-made, synthesized in the labs and factories and can be melted and cast into desired shapes are called synthetic polymers. Examples are polyethylene, PVC, bakelite, nylon etc.

Q20. What is Buna-S? How is it prepared?

Solution

Buna-S is a copolymer of butadiene and styrene. It is prepared by copolymerisation of 1,3 butadiene and styrene along with sodium.