JEE Chemistry Polymers MCQs Set 06

Answer: (c) Bakelite

Explanation:
1. Bakelite becomes a rigid cross-linked network on heating and cannot be softened again.
2. PVC, PVA and Perspex are thermoplastics.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (d) both addition and condensation polymers

Explanation:
1. Polymers are formed either by addition of monomers with no by-product or by condensation with loss of a small molecule.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (a) linear polymers

Explanation:
1. Thermoplastics have linear or slightly branched chains with no cross-links, which is why they soften repeatedly on heating.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (c) an elastic material (rubber)

Explanation:
1. Natural rubber is cis-1,4-polyisoprene and is an elastomer.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (b) a natural resin

Explanation:
1. Shellac is a hard natural resin used in varnishes and polishes.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (d) Beeswax

Explanation:
1. Beeswax is a mixture of esters of fatty acids and long-chain alcohols, not a chain of repeating units.
2. Gun cotton is cellulose nitrate, Perspex is PMMA and shellac is a polyester resin.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (d) Fat

Explanation:
1. Fat is a triester of glycerol with small fatty acids and has a definite small molecular mass.
2. Wool and leather are proteins and cotton is cellulose.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (a) thermosetting polymer

Explanation:
1. Melamine-formaldehyde resin is a cross-linked, hard, rigid thermosetting polymer.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (a) cellulose

Explanation:
1. Cellulose is a polymer of glucose found in plant cell walls.
2. The others are synthetic.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (d) all of these

Explanation:
1. Nylon, polyethylene and terylene are linear polymers that soften on heating and can be remoulded.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (d) all of these

Explanation:
1. Each is formed with loss of a small molecule such as H₂O.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (c) starch

Explanation:
1. Starch is a polymer of glucose made by plants.
2. The other three are synthetic.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (d) protein

Explanation:
1. Proteins are polymers of alpha-amino acids.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (a) low density polythene

Explanation:
1. Low density polythene is made by the free-radical route at high pressure and has many side chains.
2. High density polythene is linear.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (d) an amino acid

Explanation:
1. A polypeptide is built from amino acids joined by peptide (amide) bonds.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (b) polyethylene

Explanation:
1. Polyethylene is formed from ethylene by addition with no by-product.
2. Glucose and ethylene are not polymers and terylene is a condensation polymer.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (d) amylose

Explanation:
1. Amylose is an unbranched chain of alpha-D-glucose units.
2. Amylopectin and glycogen are branched, and starch is a mixture of amylose and amylopectin.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (d) all of these

Explanation:
1. Silk is a protein fibre, nylon-66 is a polyamide fibre and dacron is a polyester fibre.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (b) addition polymer

Explanation:
1. Natural rubber is an addition polymer of isoprene (2-methylbuta-1,3-diene).

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (c) homopolymer

Explanation:
1. Polyethylene is made from a single monomer, ethene.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (a) cellulose

Explanation:
1. Cellulose is attacked by micro-organisms.
2. Polythene, PVC and nylon-6 are synthetic and are not degraded readily.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (d) terylene

Explanation:
1. Terylene forms from terephthalic acid and ethylene glycol with loss of water.
2. The others are addition polymers.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (d) homopolymer

Explanation:
1. Nylon-66 forms from two different monomers, hexamethylenediamine and adipic acid, so it is a copolymer and not a homopolymer.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (a) terylene

Explanation:
1. Terylene is made by condensation with loss of water.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (a) thermoplastic

Explanation:
1. Polythene softens on heating and hardens on cooling repeatedly.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (c) resins

Explanation:
1. Bakelite is a hard phenol-formaldehyde resin.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (c) nylon

Explanation:
1. Nylon forms by repeated condensation between difunctional monomers.
2. The others form by chain growth.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.