Polymers

NCERT Pg. 436 (Polymer)

$\bullet$ Polythene is an example of thermoplastic polymer.

Melamine polymer, Bakelite and Urea-formaldehyde resin are thermosetting polymers.

$\bullet$ Thermoplastic polymers are the linear or slightly long chain molecules capable of repeatedly softening and hardening on cooling.

$\bullet$ Thermosetting polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross-linking in moulds and again become infusible. These cannot be reused.

$\bullet$ Elastomers have polymer chains held together by weak intermolecular forces.

$\bullet$ Fibres possess high tensile strength.

Neoprene is made by joining smaller molecules together without losing any atoms. This process is called addition polymerization.

Condensation polymers are made when small molecules, like water, are released during the reaction. Neoprene does not form this way.

So, Neoprene is not a condensation polymer.

(a) Buna - S $\longrightarrow(P)$ styrene, it is one of the monomer of buna - S, i.e. $\left[\mathrm{C}_6 \mathrm{H}_5-\mathrm{CH}=\mathrm{CH}_2\right]$

(ii) Ethylene glycol $\longrightarrow(Q)$, Trylene is made by the monomers, ethylene glycol

and terephtalic acid.

(iii) Elastomer $\longrightarrow(\mathrm{R})$, Chloroprene is an example of elastomer.

Hence, the correct match is :

(i) - P, (ii) - Q, (iii) - R

Nylon-6 is a condensation polymer, made by the monomer, caprolactum. The reaction takes place as follows:

Thus, assertion and reason both are correct and given reason is the correct for the given assertion. Hence, option (a) is the correct.

The given reaction in the question is the polymerisation reaction of nylon-6 which is shown below

Caprolactam is the monomer of nylon - 6. Thus, $X$ is caprolactam.

Both assertion and reason are correct and reason is the correct explanation of assertion. The molecular mass of large molecules is determined using the osmotic pressure technique. The molecular mass of smaller molecules is determined using the freezing point lowering method.

Assertion is correct but reason is incorrect. Most of the synthetic polymers are not biodegradable because they are not easily broken by soil organisms and are hazardous to the environment.