Q.75 Chemistry ⭐ 360° Option Elimination Active

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NEET 2021 Chemistry Question 75 Solution

Topic: Polymers · Official NTA Booklet Code M1

Question

Which one of the following polymers is prepared by addition polymerisation?

(1)Teflon
(2)Nylon-66
(3)Novolac
(4)Dacron

✓

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 ↗

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NEET 2021 Chemistry Question 75 Solution

Question

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

Step-by-Step Rigorous Workflow & Mathematical Proof

Definition of Addition Polymerisation

Preparation and Reaction of Teflon (Polytetrafluoroethene)

Analysis of Condensation Polymers

360° Option Elimination Engine Key Feature

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

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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