JEE Chemistry Polymers MCQs Set 12

Answer: (c) alpha-D-glucose

Explanation:
1. Starch consists of amylose (unbranched, alpha-1,4 links) and amylopectin (branched, alpha-1,4 and alpha-1,6 links).
2. Both are built entirely from alpha-D-glucose units.

Teacher's Note:
1. Cellulose is the beta-D-glucose polymer.
2. Starch is the storage polysaccharide of plants.

Answer: (a) Nylon-6,6

Explanation:
1. Nylon-6,6 is formed from hexamethylenediamine and adipic acid and has repeating -CO-NH- amide links.
2. Terylene has ester links, Teflon is a fluorocarbon chain and Bakelite is a phenol-formaldehyde network.

Teacher's Note:
1. Polyamides contain the -CONH- group, like proteins.
2. Polyesters contain the -COO- group.

Answer: (d) adipic acid

Explanation:
1. Nylon-6,6 is the condensation polymer of hexane-1,6-diamine and hexanedioic acid (adipic acid), both with six carbon atoms.
2. Water is eliminated at each amide link formed.

Teacher's Note:
1. The two 6s in the name are the carbon counts of the diamine and the diacid.
2. Nylon-6,10 uses sebacic acid with a 10-carbon chain.

Answer: (b) Nylon

Explanation:
1. Nylon contains amide (-CONH-) links, so it has nitrogen.
2. PVC contains chlorine, and Bakelite and Terylene contain only C, H and O.

Teacher's Note:
1. Polyamides, polyacrylonitrile and Buna-N contain nitrogen.
2. Check the monomer formulae.

Answer: (b) 1,3-butadiene and styrene

Explanation:
1. Buna-S is formed by addition copolymerisation of 1,3-butadiene (Bu) with styrene, using sodium (Na) as catalyst (S).
2. Buna-N uses acrylonitrile in place of styrene.

Teacher's Note:
1. Bu = butadiene, na = sodium, S = styrene.
2. Buna-N has N for nitrile.

Answer: (d) nylon-6

Explanation:
1. Caprolactam is a six-carbon cyclic amide.
2. On heating at 530 K with a trace of water it undergoes ring opening and polymerisation to nylon-6, whose repeating unit is -NH-(CH2)5-CO-.

Teacher's Note:
1. Nylon-6 is made from a single monomer.
2. Nylon-6,6 needs two monomers.

Answer: (a) \( \ce{(C2H5)3Al} \) with \( \ce{TiCl4} \)

Explanation:
1. The Ziegler-Natta catalyst is a combination of triethylaluminium and titanium tetrachloride.
2. It gives stereoregular, high density polyethylene and isotactic polypropylene.
3. The other three are Zeise's salt, Wilkinson's catalyst and ferrocene.

Teacher's Note:
1. Wilkinson's catalyst is used for hydrogenation.
2. Ziegler-Natta catalysts give stereoregular polymers.

Answer: (c) A-s, B-r, C-q, D-p

Explanation:
1. Bakelite is the condensation polymer of phenol and formaldehyde.
2. Polypropylene is the addition polymer of propene.
3. Glyptal is the polyester of ethylene glycol and phthalic anhydride.
4. Nylon-6 is obtained from caprolactam.

Teacher's Note:
1. Learn each polymer with its monomers.
2. Glyptal is used in paints and lacquers.

Answer: (d) Natural rubber

Explanation:
1. Natural rubber is cis-1,4-polyisoprene, built from 2-methylbuta-1,3-diene (isoprene).
2. The others contain no isoprene unit.

Teacher's Note:
1. Isoprene is 2-methyl-1,3-butadiene.
2. Neoprene is the chlorine analogue (chloroprene).

Answer: (b) Polyester

Explanation:
1. Polyesters form from a diol and a diacid with loss of water at each link.
2. Polystyrene, PVC and Teflon are addition polymers of vinyl-type monomers.

Teacher's Note:
1. Condensation polymers lose a small molecule at each step.
2. Addition polymers lose nothing.

Answer: (a) \( \ce{CH2=CH-CH=CH2} \)

Explanation:
1. Radical addition polymerisation is easiest when the growing radical is stabilised.
2. 1,3-Butadiene gives a delocalised (allylic) radical on addition, so it polymerises most readily.
3. But-1-ene gives only a secondary alkyl radical, and the alkynes are less reactive.

Teacher's Note:
1. Conjugated dienes polymerise easily.
2. The more stable the intermediate radical, the faster the chain growth.

Answer: (c) neoprene

Explanation:
1. Vinylacetylene adds HCl across the triple bond to form 2-chlorobuta-1,3-diene (chloroprene).
2. Addition polymerisation of chloroprene gives polychloroprene, called neoprene, a synthetic rubber.

Teacher's Note:
1. Neoprene is polychloroprene.
2. It resists oil and heat better than natural rubber.

Answer: (c) 3

Explanation:
1. Nylon-6, nylon-6,6 and nylon-6,10 are polyamides formed by condensation (or ring opening and condensation) polymerisation.
2. Buna-N, Buna-S, PVC, polystyrene and Teflon are addition polymers.
3. So there are 3.

Teacher's Note:
1. Count only polyamides here.
2. Nylon-6 is regarded as a condensation polymer.

Answer: (a) 4

Explanation:
1. PVC, Teflon, neoprene and Buna-S are made by addition polymerisation.
2. Terylene, nylon-6,6 and Bakelite are condensation polymers.
3. So there are 4.

Teacher's Note:
1. Addition polymers come from unsaturated monomers.
2. Condensation polymers come from bi- or poly-functional monomers.

Answer: (d) Protein, nylon-6,6 and nylon-6 only

Explanation:
1. Proteins are natural polyamides with peptide links (-CONH-).
2. Nylon-6,6 and nylon-6 are synthetic polyamides.
3. Polystyrene has a hydrocarbon backbone with no amide group.

Teacher's Note:
1. A peptide bond is an amide bond.
2. Polystyrene is an addition polymer.

Answer: (b) condensation polymerisation and copolymerisation

Explanation:
1. Water is lost in forming each amide link, so it is condensation polymerisation.
2. Two different monomers are used, so the product is a copolymer.

Teacher's Note:
1. Two different monomers mean copolymer.
2. Elimination of small molecules means condensation.

Answer: (b) Terylene, Bakelite and nylon-6,6

Explanation:
1. Terylene (polyester), Bakelite (phenol-formaldehyde) and nylon-6,6 (polyamide) are formed with loss of small molecules.
2. PVC is an addition polymer of vinyl chloride.

Teacher's Note:
1. PVC is made from chloroethene by addition.
2. Check the monomers.

Answer: (d) Ziegler-Natta catalyst, triethylaluminium with titanium tetrachloride

Explanation:
1. Ziegler-Natta catalyst is a solid TiCl4 surface activated by trialkylaluminium.
2. It polymerises ethylene at low pressure and temperature to linear high density polyethylene.
3. Peroxides are homogeneous radical initiators used in low density polyethylene.

Teacher's Note:
1. High density polyethylene needs Ziegler-Natta catalyst.
2. Low density polyethylene needs peroxide initiator at high pressure.

Answer: (a) natural rubber

Explanation:
1. Nylon and cellulose have hydrogen bonding, and PVC has dipole-dipole forces.
2. Natural rubber is a non-polar hydrocarbon polymer held only by weak van der Waals forces, hence it is an elastomer.

Teacher's Note:
1. Elastomers have the weakest forces; fibres the strongest.
2. Order: elastomer < thermoplastic < fibre.

Answer: (c) 6

Explanation:
1. Melamine is 1,3,5-triazine-2,4,6-triamine, with 3 ring nitrogen atoms and 3 amino nitrogen atoms.
2. Each nitrogen carries one lone pair, so 6 lone pairs in all (the amino lone pairs are delocalised but still counted).

Teacher's Note:
1. Count one lone pair on each nitrogen.
2. Melamine is used with formaldehyde for melamine plastics.

Answer: (d) an ethylene-propylene copolymer

Explanation:
1. Natural rubber is polyisoprene, with repeating unit -CH2-C(CH3)=CH-CH2-.
2. Hydrogenation saturates the double bond to -CH2-CH(CH3)-CH2-CH2-, which is an alternating ethylene-propylene unit.

Teacher's Note:
1. Add H2 across each C=C.
2. The saturated repeat has one propylene and one ethylene portion.

Answer: (b) D-glucose

Explanation:
1. Cellulose is a linear polymer of beta-D-glucose joined by beta-1,4 glycosidic links.
2. Acid hydrolysis breaks all links and gives only D-glucose.

Teacher's Note:
1. Starch and cellulose both give glucose on hydrolysis.
2. Sucrose gives glucose and fructose.

Answer: (a) polyamide polymer

Explanation:
1. Nylon-6,6 and nylon-6 are polyamides whose chains are held by hydrogen bonds between the -CONH- groups.
2. This gives high tensile strength suitable for fibres.

Teacher's Note:
1. Polyester fibres: Terylene.
2. Polyamide fibres: nylon.

Answer: (c) Teflon

Explanation:
1. Teflon is polytetrafluoroethylene, (-CF2-CF2-)n, with every hydrogen replaced by fluorine.
2. PVC contains chlorine, neoprene has chlorine and Thiokol is a polysulphide.

Teacher's Note:
1. Teflon: non-stick, inert.
2. Monomer: tetrafluoroethene.

Answer: (c) formaldehyde (HCHO)

Explanation:
1. Phenol and formaldehyde condense in the presence of an acid or a base catalyst to give novolac or resol, which cross-link on heating to Bakelite.

Teacher's Note:
1. Bakelite is a thermosetting polymer.
2. Used for electrical switches and handles.