Chemistry NCERT Exemplar Solutions Class 12th Chapter Fifteen

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Option (B)

Explanation: Low-density polythene is obtained from the polymerization of ethane under high pressure and temperature. Low-density polyethylene is tough, a poor conductor of electricity and has a highly branched structure.

Low-density polythene is not hard because branched structure prevents stacking and thus, reduces the intermolecular force of attraction.

So, option (B) is correct.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A)

Explanation: Dacron or Terylene is formed by the condensation polymerization of ethylene glycol and phthalic acid with the elimination of water molecules. The structure of Terylene is,

This is a multiple choice answer as classified in NCERT Exemplar

Option (C)

Explanation: PHBV (Poly beta-hydroxybutyrate co-beta-hydroxy valerate) is a biodegradable polymer. It undergoes bacterial degradation in the environment. The structure is shown as,

This is a multiple choice answer as classified in NCERT Exemplar

Option (B)

Explanation: Polyacrylonitrile is used as a wool substitute in the manufacture of commercial fibers such as orlon or acrilan.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A)

Explanation: Semi-synthetic polymers are obtained from natural polymers. Cellulose derivatives like cellulose nitrate, cellulose acetate rubber are examples of semi-synthetic polymers.

Cis-polyisoprene is not a semi-synthetic polymer while other examples are semi-synthetic polymer.

This is a multiple choice answer as classified in NCERT Exemplar

Option (D)

Explanation: Glycogen is a branched polymer of glucose found in the liver, muscles, and brain of animals.

This is a Long Answer Type Questions as classified in NCERT Exemplar

Ans: While manufacturing tyre rubber, 5 % sulfur is used as a crosslinking agent. A natural linear polymer of 2-methyl-1, 3-butadiene becomes hard on treatment with sulfur and forms vulcanised rubber. The structure of the product formed is,

This is a Long Answer Type Questions as classified in NCERT Exemplar

Thermoplastic polymer

Thermoplastic polymers are linear or slight branched-chain polymers. In this type of polymer, the strong intermolecular force of attraction is present between elastomers and fibers. This type of polymer softens on heating and hardens on cooling. For example, polythene, polystyrene and polyvinyl.

Thermosetting polymer

Thermosetting polymers are cross-linked polymers. These polymers on heating undergo cross-linking in molds. They become infusible on heating so, cannot be reused again. For example, Bakelite and urea-formaldehyde resins.

This is a Long Answer Type Questions as classified in NCERT Exemplar

Ans: