Select the correct option to match the Polymer to its Major polymeric constituent from the table given below:PolymerMajor polymeric constituentPNatural rubberIPolyisobutyleneQGutta perchaIIPolychloropreneRNeopreneIIItrans-1,4-polyisopreneSButyl rubberIVcis-1,4-polyisoprene

The correct matching is P-IV ; Q-III ; R-II ; S-I.Natural rubber is cis-1,4-polyisoprene, which is amorphous and elastic at room temperature (IV).Gutta percha is trans-1,4-polyisoprene, which crystallises and is hard and leathery (III).Neoprene is polychloroprene (II).Butyl rubber is mainly polyisobutylene, with a little isoprene for vulcanisation (I).Option A swaps neoprene and butyl rubber. The options pairing natural rubber with polychloroprene confuse a synthetic rubber with the natural one.

Classification of Polymers Questions and Answers

Q: Which one of the following polymers occurs naturally?

The natural polymer is cellulose.Cellulose, a linear polysaccharide of β-1,4-linked glucose units, is made by plants and is the main structural material of cell walls, cotton and wood.The others are synthetic. Bakelite is a phenol-formaldehyde thermoset, the first fully synthetic plastic. Teflon is polytetrafluoroethylene, made from tetrafluoroethylene. Perspex is poly(methyl methacrylate), the acrylic glass made by polymerising methyl methacrylate.

Q: Which one of the monomers given is used in the synthesis of cellulose?

Cellulose is built from Glucose.Cellulose is a linear polysaccharide of D-glucose units joined by \(\beta\)-1,4-glycosidic links. The \(\beta\) linkage lets the chains lie straight and hydrogen-bond into fibrils, which is why cellulose is strong and insoluble, unlike starch, which is also made of glucose but with \(\alpha\) links.Fructose is the monomer of inulin-type fructans and, with glucose, makes sucrose. Galactose is found in lactose, agar and galactomannans. Lactic acid is the monomer of polylactic acid (PLA), a synthetic polyester, not a polysaccharide.

Q: What is the correct order of decreasing crystallinity of the given polymers?P atactic-PolypropyleneQ syndiotactic-PolystyreneR Nylon 6S Polyethylene terephthalate

The key gives option D: PET > Nylon 6 > syndiotactic polystyrene > atactic polypropylene. I could confirm only the last place with certainty; I could not confirm the order of the other three with a handbook source.Atactic polypropylene (P) has its methyl groups placed at random, cannot pack into a lattice and is amorphous, so it is last. This rules out options A, B and C, which each place P above at least one crystallisable polymer. Syndiotactic polystyrene (Q) is regular and does crystallise, but the bulky phenyl rings make it crystallise slowly. Nylon 6 (R) and PET (S) are the classic semicrystalline polymers.The order of PET and Nylon 6 in particular depends on the thermal and mechanical history of the sample and on how crystallinity is measured, and the order of the middle three can differ between sources. The key’s ranking is the usual textbook one; the explanation records it as the official answer and not as something I verified in a reference table.

Q: Polymer “Z” has a high melting point and it decomposes even before it melts. Hence, it is usually dissolved and subsequently regenerated. Rayon is one such regenerated form. Identify the polymer “Z” from the following options.

Polymer Z is cellulose.Cellulose chains are held together by dense hydrogen bonding between their hydroxyl groups, so the polymer degrades before it can melt. It therefore cannot be melt-processed. Instead it is dissolved (for example as cellulose xanthate in the viscose process) and regenerated as fibre or film. Viscose rayon and cellophane are regenerated cellulose.Urea formaldehyde is a thermosetting resin that cures in a mould; it is not dissolved and regenerated into fibres. Poly(vinyl carbazole) and poly(vinyl acetate) are thermoplastics that soften on heating, and neither is the parent of rayon.

Q: The carboxylic acid that is used in rubber, textile, dyeing, leather and electroplating industries is

The acid is methanoic acid (formic acid).Methanoic acid is used in the rubber industry (to coagulate latex), and in the textile, dyeing, leather and electroplating industries; this list of uses is given for it in the standard textbook account of carboxylic acids.Ethanoic acid is used mainly as vinegar and as a solvent; lactic acid in foods and pharmaceuticals; benzoic acid (as sodium benzoate) as a food preservative; and hexanoic acid in making esters for flavours.

Q: Based on tacticity, the polymer is divided into .................... types.

By tacticity polymers are divided into three types.Tacticity describes the relative configuration of successive stereocentres along a chain such as polypropylene:Isotactic: all substituents on the same side of the extended backbone.Syndiotactic: substituents alternate regularly from one side to the other.Atactic: substituents placed at random.Ziegler-Natta and metallocene catalysts are valued precisely because they give isotactic or syndiotactic polymers, which crystallize, while radical polymerization usually gives atactic material. Two, four and five do not match this standard classification.

The crystalline melting temperature of the polymers high density polyethylene (HDPE), isotactic polypropylene (iPP), nylon 6 (PA6) and poly(ethylene terephthalate) (PET) can be arranged as

A.\(T_{HDPE} \gt T_{PET} \gt T_{iPP} \gt T_{PA6}\)
B.\(T_{PET} \gt T_{PA6} \gt T_{iPP} \gt T_{HDPE}\)
C.\(T_{PA6} \gt T_{HDPE} \gt T_{PET} \gt T_{iPP}\)
D.\(T_{iPP} \gt T_{PA6} \gt T_{PET} \gt T_{HDPE}\)

Exam Year(s)

GATE XE - 2012,

Answer: B

The order is \(T_{PET} \gt T_{PA6} \gt T_{iPP} \gt T_{HDPE}\).

Typical crystalline melting points are about 260°C for PET, 220°C for nylon 6, 165°C for isotactic polypropylene and 130-135°C for HDPE.

The aromatic rings in the PET backbone stiffen the chain and the hydrogen bonding between amide groups holds nylon chains together, so both melt high. Polypropylene's methyl groups stiffen its helix compared with polyethylene, whose flexible, non-polar chains melt lowest. The other orders put HDPE or iPP above the polar or aromatic polymers, which is the reverse of the actual trend.

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Which one of the following polymers occurs naturally?

A.Bakelite
B.Teflon
C.Cellulose
D.Perspex

Exam Year(s)

GATE XE - 2018,

Answer: C

The natural polymer is cellulose.

Cellulose, a linear polysaccharide of β-1,4-linked glucose units, is made by plants and is the main structural material of cell walls, cotton and wood.

The others are synthetic. Bakelite is a phenol-formaldehyde thermoset, the first fully synthetic plastic. Teflon is polytetrafluoroethylene, made from tetrafluoroethylene. Perspex is poly(methyl methacrylate), the acrylic glass made by polymerising methyl methacrylate.

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Which one of the monomers given is used in the synthesis of cellulose?

A.Fructose
B.Lactic acid
C.Galactose
D.Glucose

Exam Year(s)

GATE XE - 2023,

Answer: D

Cellulose is built from Glucose.

Cellulose is a linear polysaccharide of D-glucose units joined by \(\beta\)-1,4-glycosidic links. The \(\beta\) linkage lets the chains lie straight and hydrogen-bond into fibrils, which is why cellulose is strong and insoluble, unlike starch, which is also made of glucose but with \(\alpha\) links.

Fructose is the monomer of inulin-type fructans and, with glucose, makes sucrose. Galactose is found in lactose, agar and galactomannans. Lactic acid is the monomer of polylactic acid (PLA), a synthetic polyester, not a polysaccharide.

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What is the correct order of decreasing crystallinity of the given polymers?

P atactic-Polypropylene
Q syndiotactic-Polystyrene
R Nylon 6
S Polyethylene terephthalate

A.\(P \gt R \gt S \gt Q\)
B.\(S \gt Q \gt P \gt R\)
C.\(Q \gt S \gt R \gt P\)
D.\(S \gt R \gt Q \gt P\)

Exam Year(s)

GATE XE - 2023,

Answer: D

The key gives option D: PET > Nylon 6 > syndiotactic polystyrene > atactic polypropylene. I could confirm only the last place with certainty; I could not confirm the order of the other three with a handbook source.

Atactic polypropylene (P) has its methyl groups placed at random, cannot pack into a lattice and is amorphous, so it is last. This rules out options A, B and C, which each place P above at least one crystallisable polymer. Syndiotactic polystyrene (Q) is regular and does crystallise, but the bulky phenyl rings make it crystallise slowly. Nylon 6 (R) and PET (S) are the classic semicrystalline polymers.

The order of PET and Nylon 6 in particular depends on the thermal and mechanical history of the sample and on how crystallinity is measured, and the order of the middle three can differ between sources. The key’s ranking is the usual textbook one; the explanation records it as the official answer and not as something I verified in a reference table.

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Polymer “Z” has a high melting point and it decomposes even before it melts. Hence, it is usually dissolved and subsequently regenerated. Rayon is one such regenerated form. Identify the polymer “Z” from the following options.

A.Urea formaldehyde
B.Poly(vinyl carbazole)
C.Cellulose
D.Poly(vinyl acetate)

Exam Year(s)

GATE XE - 2025,

Answer: C

Polymer Z is cellulose.

Cellulose chains are held together by dense hydrogen bonding between their hydroxyl groups, so the polymer degrades before it can melt. It therefore cannot be melt-processed. Instead it is dissolved (for example as cellulose xanthate in the viscose process) and regenerated as fibre or film. Viscose rayon and cellophane are regenerated cellulose.

Urea formaldehyde is a thermosetting resin that cures in a mould; it is not dissolved and regenerated into fibres. Poly(vinyl carbazole) and poly(vinyl acetate) are thermoplastics that soften on heating, and neither is the parent of rayon.

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Select the correct option to match the Polymer to its Major polymeric constituent from the table given below:

Polymer		Major polymeric constituent
P	Natural rubber	I	Polyisobutylene
Q	Gutta percha	II	Polychloroprene
R	Neoprene	III	trans-1,4-polyisoprene
S	Butyl rubber	IV	cis-1,4-polyisoprene

A.P-IV ; Q-III ; R-I ; S-II
B.P-IV ; Q-III ; R-II ; S-I
C.P-II ; Q-IV ; R-I ; S-III
D.P-II ; Q-IV ; R-III ; S-I

Exam Year(s)

GATE XE - 2026,

Answer: B

The correct matching is P-IV ; Q-III ; R-II ; S-I.

Natural rubber is cis-1,4-polyisoprene, which is amorphous and elastic at room temperature (IV).
Gutta percha is trans-1,4-polyisoprene, which crystallises and is hard and leathery (III).
Neoprene is polychloroprene (II).
Butyl rubber is mainly polyisobutylene, with a little isoprene for vulcanisation (I).

Option A swaps neoprene and butyl rubber. The options pairing natural rubber with polychloroprene confuse a synthetic rubber with the natural one.

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The carboxylic acid that is used in rubber, textile, dyeing, leather and electroplating industries is

A.methanoic acid
B.ethanoic acid
C.lactic acid
D.benzoic acid
E.hexanoic acid

Exam Year(s)

KEAM - 2026,

Answer: A

The acid is methanoic acid (formic acid).

Methanoic acid is used in the rubber industry (to coagulate latex), and in the textile, dyeing, leather and electroplating industries; this list of uses is given for it in the standard textbook account of carboxylic acids.

Ethanoic acid is used mainly as vinegar and as a solvent; lactic acid in foods and pharmaceuticals; benzoic acid (as sodium benzoate) as a food preservative; and hexanoic acid in making esters for flavours.

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Based on tacticity, the polymer is divided into .................... types.

A.Two
B.Four
C.Three
D.Five

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: C

By tacticity polymers are divided into three types.

Tacticity describes the relative configuration of successive stereocentres along a chain such as polypropylene:

Isotactic: all substituents on the same side of the extended backbone.
Syndiotactic: substituents alternate regularly from one side to the other.
Atactic: substituents placed at random.

Ziegler-Natta and metallocene catalysts are valued precisely because they give isotactic or syndiotactic polymers, which crystallize, while radical polymerization usually gives atactic material. Two, four and five do not match this standard classification.

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