JEE Main 2020 · 6 September · morning · Single correct · +4 / −1
Consider the Assertion and Reason given below.
Assertion (A) : Ethene polymerized in the presence of Ziegler Natta Catalyst at high temperature and pressure is used to make buckets and dustbins.
Reason (R) : High density polymers are closely packed and are chemically inert.
Choose the correct answer from the following:
- (a) Both (A) and (R) are correct and (R) is the correct explanation of (A).
- (b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
- (c) (A) is correct but (R) is wrong.
- (d) (A) and (R) both are wrong.
Answer and solution
Answer (a) Both (A) and (R) are correct and (R) is the correct explanation of (A).
Solution
Chemistry ma’am · 3 steps
The Ziegler–Natta catalyst tells you this is HDPE, and its packing explains why buckets are made from it.
- Identify the polymer. Ethene polymerised with a Ziegler–Natta catalyst (triethylaluminium with titanium tetrachloride) gives high density polythene, HDPE. Without this catalyst, ethene polymerised with traces of oxygen or a peroxide gives the low density form, LDPE.
Property LDPE HDPE Made using traces of O₂ or a peroxide Ziegler–Natta catalyst Chain shape highly branched linear Packing and nature loose, soft and flexible closely packed, tough, chemically inert Used for squeeze bottles, toys, flexible pipes buckets, dustbins, bottles, pipes - Check the reason. HDPE chains are linear, so they pack closely. This makes the polymer dense, hard and tough, and it also makes it chemically inert. A bucket or dustbin needs to be rigid and must not react with whatever it holds.
- So. (A) is correct, (R) is correct, and the close packing and inertness in (R) are exactly why HDPE is used for buckets and dustbins. The answer is (a).
The idea to keep. For polythene, the catalyst decides the form. Ziegler–Natta gives linear, closely packed, tough HDPE. Peroxide gives branched, soft LDPE. Match the structure to the use.
Answer from the NTA final answer key. Solution by PrepWiser.