PolymersNEET Chemistry · Class 12 · NCERT Chapter 11

Solution

Option (d) represents a phenol-formaldehyde resin, which is a thermosetting polymer. Thermosetting polymers, like Bakelite, are formed by the condensation of phenol and formaldehyde and do not melt on heating but decompose, as described in NCERT XII chapter Polymers.

Solution

Dacron, a polyester, is formed by the polymerization of terephthalic acid and ethylene glycol. This reaction is a typical condensation polymerization, as described in NCERT XII chapter Polymers, making option (c) correct.

Solution

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Solution

Natural rubber consists of polymerized isoprene units with all cis-configuration, which gives it elasticity and flexibility. NCERT XII chapter Polymers describes natural rubber as a cis-1,4-polyisoprene, so option (a) is correct.

Solution

Cross-linked or network polymers are formed from monomers with at least two functional groups, not bi- and tri-functional monomers. Examples include bakelite and melamine, which contain covalent bonds between polymer chains and within the chains. Therefore, option (b) is incorrect.

Solution

𝐶𝑎(𝑂𝐻)2=𝐶𝑎+2+2𝑂𝐻− 𝑝𝐻= 9, so pOH = 5, so [𝑂𝐻−]=10−5 M at equilibrium, [𝑂𝐻−]=10−5 M [𝐶𝑎+2]=0.5×10−5 M 𝐾𝑆𝑃=[𝐶𝑎+2][𝑂𝐻−]2= ( 1 2×10−5)×(10−5)2= 0.5×10−15

Solution

cis-1,4-polyisoprene is the natural polymer found in rubber latex, derived from rubber trees. Other options are synthetic polymers, so option (a) is correct.

Solution

Teflon (polytetrafluoroethylene) is prepared by addition polymerisation of tetrafluoroethylene. Nylon-66, Novolac, and Dacron are formed by condensation polymerisation, so option (a) is correct.

Solution

• Thermoplastic polymers are the linear or slightly long chain molecules capable of repeatedly softening and hardening on cooling. • 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. • Elastomers have polymer chains held together by weak intermolecular forces. • Fibres possess high tensile strength.

Solution

Neoprene is produced by the polymerization of chloroprene, whose monomer structure is ${\text{H}}_2\text{C}=\text{C}(\text{Cl})-\text{CH}={\text{CH}}_2$. NCERT XII chapter Polymers lists chloroprene as the monomer for neoprene, so option (c) is correct.