JEE Main 2023 · 11 April · evening · Single correct · +4 / −1

Given below are two statements :
Statement I : Ethene at 333 to 343 K and 6-7 atm pressure in the presence of AlEt₃ and TiCl₄ undergoes addition polymerization to give LDP.
Statement II : Caprolactam at 533-543 K in H₂ O through step growth polymerizes to give Nylon 6.
In the light of the above statements, choose the correct answer from the options given below:

  1. (a) Both Statement I and Statement II are true
  2. (b) Statement I is true but Statement II is false
  3. (c) Statement I is false but Statement II is true
  4. (d) Both Statement I and Statement II are false
Answer and solution

Answer (c) Statement I is false but Statement II is true

Solution

Chemistry ma’am · 3 steps

Ziegler–Natta catalyst with ethene gives straight chains, so the product is HDPE, not LDP.

  1. Statement I. AlEt₃ with TiCl₄ is the Ziegler–Natta catalyst. At 333 to 343 K and 6 to 7 atm it adds ethene units into straight, unbranched chains that pack closely. That polymer is high density polythene (HDP), so Statement I is false.
    PolytheneConditionsChain shape
    LDP350 to 570 K, 1000 to 2000 atm, traces of O₂ or a peroxide (free radical)highly branched
    HDP333 to 343 K, 6 to 7 atm, AlEt₃ + TiCl₄ (Ziegler–Natta)linear
  2. Statement II. Caprolactam heated with water at 533 to 543 K opens its ring and joins up through amide links, one step at a time. This is step growth (condensation) polymerisation, and the product is Nylon 6. Statement II is true.
  3. So. Statement I is false and Statement II is true, which is option (c).

The idea to keep. For polythene, match the conditions. High pressure with a free radical initiator gives branched LDP. Low pressure with the Ziegler–Natta catalyst gives linear HDP.

Answer from the NTA final answer key. Solution by PrepWiser.

Study Polymers

Asked about 50 times in JEE Main since 2020. This question is from 2023.