🧪 Chemistry Moderate Frequency

NEET Polymers Previous Year Questions with Solutions

Complete repository of official NTA NEET questions for Polymers from 2020 to 2026. Every question includes 30-second elimination tricks, step-by-step NCERT solutions, option-by-option traps, and official answer keys.

3 Questions 3 Exam Years (2023, 2021, 2020) 3 Easy · 0 Medium · 0 Challenging

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NEET 2023 · Q59 Easy Free Radical Polymerization of Chloroprene to Form Neoprene

Dedicated Page ↗

Official NEET 2023 Question 59 - Polymers

3 ✓ Key

💡 Verified Solution & 30-Second Hack

✓

Verified Against NTA Final Answer Key

Option (3) : H₂C = C(Cl) – CH = CH₂ (Chloroprene)

📚 Polymers Easy

📋 Given Parameters & Problem Setup

Target polymer Neoprene (Polychloroprene)

Monomer class Conjugated diene derivative

⚡

The 30-Second Exam Hall Shortcut: ⚡ Rubber Monomer Match Hack: Neo = Chloro!

⏱️ Save ~25 seconds

Natural rubber is polyisoprene (methyl group at C-2). Synthetic Neoprene is polychloroprene (chlorine atom at C-2: H₂C = C(Cl)–CH = CH₂). Instant Option (3) in 5 seconds!

1 Recall common conjugated diene monomers:

2 - Isoprene: H₂C = C(CH₃)–CH = CH₂ ⟶ Natural rubber (cis-1,4-polyisoprene).

3 - 1,3-Butadiene: H₂C = CH–CH = CH₂ ⟶ Buna-S / Buna-N copolymer component.

4 - Chloroprene: H₂C = C(Cl)–CH = CH₂ ⟶ Neoprene (synthetic rubber).

5 Match the structure of chloroprene: 2-chlorobuta-1,3-diene, which is Option (3).

6 Select Option (3) directly!

🛡️

Why You Can 100% Trust This Shortcut: Polymer Chemistry · Monomers of Synthetic Rubbers (Neoprene is commercially prepared by the free radical polymerization of chloroprene, 2-chlorobuta-1,3-diene).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Identification of Neoprene

Neoprene (polychloroprene) is a synthetic elastomer with superior resistance to vegetable and mineral oils. It is synthesized by the addition polymerization of its monomer in the presence of oxygen or peroxide catalysts:

n\, \text{H}_2\text{C}=\overset{\text{Cl}}{\text{C}}-\text{CH}=\text{CH}_2 \xrightarrow{\text{Polymerization}} \left[ -\text{CH}_2-\overset{\text{Cl}}{\text{C}}=\text{CH}-\text{CH}_2- \right]_n

Step 2

IUPAC and Common Nomenclature of the Monomer

The monomer shown in Option (3) is 2-chlorobuta-1,3-diene, commonly known as chloroprene:

\text{Chloroprene: } \text{H}_2\text{C}=\text{C}(\text{Cl})-\text{CH}=\text{CH}_2

Step 3

Contrast with Other Diene Monomers

Differentiating the structures of the dienes provided in the options:

\begin{aligned} \text{Option 1: } &\text{H}_2\text{C}=\text{C}(\text{CH}_3)-\text{CH}=\text{CH}_2 \quad (\text{Isoprene } \longrightarrow \text{Natural Rubber}) \\[4pt] \text{Option 2: } &\text{H}_2\text{C}=\text{CH}-\text{CH}=\text{CH}_2 \quad (\text{Buta-1,3-diene } \longrightarrow \text{Polybutadiene}) \\[4pt] \text{Option 3: } &\text{H}_2\text{C}=\text{C}(\text{Cl})-\text{CH}=\text{CH}_2 \quad (\text{Chloroprene } \longrightarrow \text{Neoprene}) \\[4pt] \text{Option 4: } &\text{H}_2\text{C}=\text{CH}-\text{C}\equiv\text{CH} \quad (\text{Vinylacetylene}) \end{aligned}

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 (1)

✗ Incorrect

Verdict & Scientific Reason:

Isoprene: monomer of natural rubber, not neoprene.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate confused isoprene with chloroprene.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

1,3-Butadiene: monomer of polybutadiene and Buna rubbers.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate selected unsubstituted butadiene.

3 (3)

✓ 100% Correct

Verdict & Scientific Reason:

Chloroprene (2-chlorobuta-1,3-diene): monomer of neoprene.

💡

Why this is airtight: None. Candidate knew the structure of chloroprene.

4 (4)

✗ Incorrect

Verdict & Scientific Reason:

Vinylacetylene: raw material used in synthesis of chloroprene, not the monomer itself.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate confused the industrial precursor with the actual polymerization monomer.

⚠️

NTA Trap Alert: Confusing Isoprene (Natural Rubber) with Chloroprene (Neoprene)

Isoprene has a -CH₃ group at C-2, forming natural rubber. Chloroprene has a -Cl group at C-2, forming neoprene. Mixing up -CH₃ and -Cl leads directly to picking Option (1).

🛡️ How to avoid the -1 mark: Memory Hook: "Chloro-prene makes Neo-prene" (both end in -prene, and chloro matches neoprene).

📖

Core NEET Syllabus Standard

National Eligibility cum Entrance Test (NEET UG) · Polymers Standard Benchmark

Core Scientific Principle Tested:

"Neoprene is formed by the free radical polymerization of chloroprene (2-chlorobuta-1,3-diene)."

Syllabus Focus: Synthetic Rubbers – Neoprene

Preserved in Rationalized Curriculum Syllabus & Academic Standards ↗

NEET 2021 · Q75 Easy Addition vs. Condensation Polymerisation: Preparation of Teflon

Dedicated Page ↗

Official NEET 2021 Question 75 - Polymers

1 Teflon ✓ Key

2 Nylon-66

3 Novolac

4 Dacron

💡 Verified Solution & 30-Second Hack

✓

Verified Against NTA Final Answer Key

Option (1) : Teflon

📚 Polymers Easy

📋 Given Parameters & Problem Setup

Polymerisation Mechanism Addition polymerisation (chain growth)

⚡

The 30-Second Exam Hall Shortcut: ⚡ Monomer with C=C Double Bond = Addition Polymer!

⏱️ Save ~20 seconds

Addition polymers form by repeated addition of unsaturated monomers containing double bonds without elimination of small molecules. Teflon (polytetrafluoroethene) is prepared from tetrafluoroethene ( $CF_2=CF_2$ ). Nylon-66, Novolac, and Dacron are all CONDENSATION polymers involving loss of $H_2O$ ! Match Option (1)!

1 Addition polymer: Formed from monomers with double/triple bonds with no byproduct.

2 Check Teflon:

n CF_2=CF_2 \xrightarrow{\text{catalyst}} -[CF_2-CF_2]_n-

\implies

Pure addition polymer.

3 Check Nylon-66: Hexamethylenediamine + adipic acid

\to

Condensation polymer (eliminates

H_2O

4 Check Novolac: Phenol + formaldehyde

\to

Condensation polymer (eliminates

H_2O

5 Check Dacron (Terylene): Ethylene glycol + terephthalic acid

\to

Condensation polymer (eliminates

H_2O

6 Match Option (1) Teflon.

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Polymers classification based on mode of polymerisation.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Definition of Addition Polymerisation

Addition (chain-growth) polymerisation involves repeated addition of monomer molecules possessing double or triple bonds to a growing polymer chain, usually in the presence of free-radical initiators, without the elimination of any small molecular byproducts like water, alcohol, or ammonia.

Step 2

Preparation and Reaction of Teflon (Polytetrafluoroethene)

Teflon is manufactured by heating tetrafluoroethene with a free radical or persulphate catalyst at high pressures:

n\,\text{CF}_2=\text{CF}_2 \xrightarrow[\text{High pressure}]{\text{Persulphate catalyst}} -[\text{CF}_2-\text{CF}_2]_n- \quad (\mathbf{\text{Addition Polymer}})

Step 3

Analysis of Condensation Polymers

- Nylon-66: Formed by condensation of hexamethylenediamine and adipic acid with elimination of $H_2O$ (polyamide condensation polymer). - Novolac: Linear condensation product of phenol and formaldehyde with loss of $H_2O$ . - Dacron (Terylene): Formed by condensation of ethylene glycol and terephthalic acid with elimination of $H_2O$ (polyester condensation polymer).

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 1

✓ 100% Correct

Verdict & Scientific Reason:

Formed strictly by addition polymerisation of tetrafluoroethene ( $CF_2=CF_2$ ).

💡

Why this is airtight: None; textbook polymer classification.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Condensation polyamide polymer eliminating water molecules.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing step-growth condensation with chain-growth addition.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Condensation polymer formed from phenol and formaldehyde.

⚠️

Student Fallacy (Why candidates pick this trap): Misclassifying phenol-formaldehyde resins.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Condensation polyester polymer eliminating water.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing polyester condensation with addition.

⚠️

NTA Trap Alert: Polyamide/Polyester Condensation vs. Addition Trap

Students frequently mix up Nylon-66 and Dacron with addition polymers because they are common synthetic fibers. Nylon-66 and Dacron are both classic CONDENSATION polymers (step-growth). Teflon is an ADDITION polymer.

🛡️ How to avoid the -1 mark: Identify the monomer:

CF_2=CF_2

has a

C=C

double bond

\implies

Addition polymer.

📖

Core NEET Syllabus Standard

NCERT Chemistry · Polymers Standard Benchmark

Core Scientific Principle Tested:

"Teflon is manufactured by addition polymerisation of tetrafluoroethene with a free radical catalyst under high pressure."

Syllabus Focus: Addition Polymers (Polytetrafluoroethene / Teflon)

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

NEET 2020 · Q119 Easy Natural vs Synthetic Polymers: Natural Rubber as cis-1,4-Polyisoprene

Dedicated Page ↗

Official NEET 2020 Question 119 - Polymers

1 cis-1,4-polyisoprene ✓ Key

2 poly (Butadiene-styrene)

3 polybutadiene

4 poly (Butadiene-acrylonitrile)

💡 Verified Solution & 30-Second Hack

✓

Verified Against NTA Final Answer Key

Option (1) : cis-1,4-polyisoprene

📚 Polymers Easy

📋 Given Parameters & Problem Setup

Classification Natural polymer

Candidate Polymers cis-1,4-polyisoprene, poly(Butadiene-styrene), polybutadiene, poly(Butadiene-acrylonitrile)

⚡

The 30-Second Exam Hall Shortcut: ⚡ "Natural Rubber = cis-1,4-Polyisoprene; Buna-S & Buna-N are Synthetic!"

⏱️ 15 seconds

Natural rubber extracted from the latex of rubber trees (Hevea brasiliensis) is chemically cis-1,4-polyisoprene. Poly(butadiene-styrene) is Buna-S, poly(butadiene-acrylonitrile) is Buna-N, and polybutadiene is synthetic rubber. Mark cis-1,4-polyisoprene (Option 1) in 5 seconds!

1 Natural rubber is a natural elastomer.

2 Chemical identity of natural rubber: cis-1,4-polyisoprene.

3 Buna-S [poly(butadiene-styrene)] = Synthetic rubber.

4 Buna-N [poly(butadiene-acrylonitrile)] = Synthetic rubber.

5 Polybutadiene = Synthetic elastomer.

6 Select Option (1) cis-1,4-polyisoprene.

🛡️

Why You Can 100% Trust This Shortcut: NCERT Chemistry · Polymers (Natural Rubber: cis-1,4-polyisoprene)

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Identify Source and Chemistry of Natural Rubber

Natural rubber is a natural polymer obtained as latex from the bark of the rubber tree. It possesses remarkable elastic properties and is classified as an elastomer.

Step 2

Stereochemistry of Natural Rubber

Natural rubber is a linear polymer of isoprene (2-methyl-1,3-butadiene). All the double bonds in the polymer chain possess the cis-configuration, making it cis-1,4-polyisoprene: $\text{Natural Rubber} = \text{cis-1,4-polyisoprene}$ The cis-configuration prevents close crystal packing and keeps intermolecular forces weak, giving rubber its elasticity. (In contrast, trans-1,4-polyisoprene is Gutta-percha).

Step 3

Evaluate Synthetic Rubbers in Options

- poly(Butadiene-styrene): Synthetic copolymer known commercially as Buna-S or SBR. - poly(Butadiene-acrylonitrile): Synthetic copolymer known commercially as Buna-N. - polybutadiene: Synthetic homopolymer synthesized by Ziegler-Natta polymerization of butadiene.

Step 4

Conclude Option 1

cis-1,4-polyisoprene is the only naturally occurring polymer among the choices.

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✓ 100% Correct

Verdict & Scientific Reason:

Factually exact; cis-1,4-polyisoprene is the chemical identity of natural rubber.

💡

Why this is airtight: None; textbook polymer definition.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; this is Buna-S, a man-made synthetic elastomer.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing synthetic rubber (Buna-S) with natural rubber.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; polybutadiene is an industrially synthesized elastomer.

⚠️

Student Fallacy (Why candidates pick this trap): Assuming simple diene polymers are natural.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; this is Buna-N, a synthetic oil-resistant elastomer.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing Buna-N with natural rubber.

⚠️

NTA Trap Alert: cis vs trans Polyisoprene

- cis-1,4-polyisoprene = NATURAL RUBBER (elastic). - trans-1,4-polyisoprene = GUTTA-PERCHA (rigid, non-elastic). - Buna-S & Buna-N = SYNTHETIC rubbers.

🛡️ How to avoid the -1 mark: Natural rubber = CIS-1,4-polyisoprene!

📖