This set of Chemistry Multiple Choice Questions for IIT JEE Exam focuses on “Types of Polymerisation Reactions – 2”.
1. What is the polymer obtained from the condensation of NH2-(CH2)6-NH2 and COOH-(CH2)8-COOH?
Explanation: Nylons are polyamides obtained from the condensation between amines and dicarboxylic acids. The have amide linkages (NHCO). Hexamethylenediamine and sebacic acid from the polymer nylon-6,10.
2. Cyclohexanone on treatment with hydroxylamine gives P, which on treatment with sulphuric acid gives Q. When Q is heated with water at high temperature, R is obtained. Identify R.
c) Amino caproic acid
Explanation: Nylon-6 is the polymer of caprolactam (Q), which is obtained from the oxidation of cyclohexane to give cyclohexanone(P), followed by treatment with H2SO4. Caprolactam on heating with water gives amino caproic acid which polymerises to nylon-6.
3. Glyptal is obtained from the condensation polymerisation of ethylene glycol with _______
a) terephthalic acid
b) phthalic acid
c) isophthalic acid
d) trimesic acid
Explanation: Glyptal is a polyester (containing COO linkages) obtained from the polycondensation reaction of ethane-1,2-diol and benzene-1,2-dicarboxylic acid (phthalic acid). It is cross-linked polymer.
4. Which of the following is not required for the production of dacron?
a) 450K temperature
b) Ethylene glycol
c) Terephthalic acid
d) Triethylaluminium-titanium tetrachloride
Explanation: Dacron or terylene is a polyester of ethylene glycol and terephthalic acid. It is produced by heating the two at 420-460K and in the presence of zinc acetate-antimony trioxide, which acts as a catalyst. On the other hand, triethylaluminium-tetrachloride is used in the synthesis of HDPE.
Explanation: The compound shown is a heterocyclic triamine called melamine. It reacts with methanal to form a resin intermediate which polymerises to form a melamine-formaldehyde polymer.
6. Bakelite is a cross-linked polymer.
Explanation: Phenol-formaldehyde condensation initially forms a linear polymer, Novolac. This on further heating with formaldehyde undergoes cross-linking through CH2 groups to form bakelite.
7. Which of the following phenols are able to form Novolac?
a) m-Hydroxybenzyl alcohol
b) o-Hydroxybenzyl alcohol and p-hydroxybenzyl alcohol
Explanation: Novolac is a linear chain phenol-formaldehyde polymer. The ortho and para hydroxy derivatives of benzyl alcohol, initially formed by the reaction of phenol with HCHO, further react with phenol to form compounds having benzene rings joined together by -CH2– links (Novolac).
a) chain growth copolymer
b) step growth copolymer
c) chain growth homopolymer
d) step growth homopolymer
Explanation: The polymer shown is butadiene-styrene copolymer which is formed by the addition polymerisation of two different unsaturated compounds, 1,3-butadiene and styrene. It is tough and used as a substitute for natural rubber.
9. The polymer of type [-AAAABBBAAAABBB-]n, where A and B are two different monomers, is called a ______ copolymer.
Explanation: Bock copolymers are those in which blocks of each type of monomer alternate with each other. In this case, the block AAAA and block BBB are alternatively repeated after each other.
10. Which of the following is the monomer of natural rubber?
Explanation: Isoprene (or 2-methyl-1,3-butadiene) repeats itself in a linear chain to form natural rubber. This is also called as cis-1,4-polyisoprene, in which the monomers are linked by weak van der Waals forces, thus making it elastic in nature.
11. Which of the following is incorrect regarding natural rubber?
a) Shows thermoplastic behaviour
b) Soluble in benzene
c) Resistant to attack by oxidising agents
d) Shows high water absorption capacity
Explanation: Natural rubber becomes soft at temperatures above 335K and shows brittle character at temperatures below 283K. Hence, it shows thermoplastic behaviour. It is soluble in non-polar solvents like benzene, toluene, etc. and is not susceptible to attack by oxidising agents.
12. Vulcanization is carried out with which element?
Explanation: Vulcanization is a process of improving the physical properties of natural rubber by introducing sulphur cross-links at the reactive sites of double bonds. This is done by heating the rubber with sulphur and an additive.
13. X on polymerisation gives neoprene. Identify X.
Explanation: Neoprene or polyisoprene is a synthetic rubber obtained from the addition polymerisation of chloroprene (2-chloro-1,3-butadiene) through free radical mechanism. It has a better stability towards oxidation than natural rubber.
14. Buna-N involves acrylonitrile as one of the monomers.
Explanation: Buna-N is a nitrile rubber formed by the copolymerisation of 1,3-butadiene and acrylonitrile. On the other hand, buna-S is a styrene rubber, with vinylbenzene as one monomer in place of acrylonitrile.
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