The polymer X - consists of linear molecules and is closely packed. It is prepared in the presence of triethylaluminium and titanium tetrachloride under low pressure. The polymer X is-

Solution

Chemistry ma’am · 3 steps

Ziegler-Natta catalyst at low pressure means ethene chains grow straight, pack tightly, and give HDPE.

1. Spot the catalyst. Triethylaluminium with titanium tetrachloride, (C₂H₅)₃Al + TiCl₄, is the Ziegler-Natta catalyst. With ethene it works at low pressure and about 333 to 343 K.
2. Linear chains. This catalyst adds ethene units one after another without side branches. Unbranched chains can line up close to each other, so the polymer is closely packed and has high density.

   Polymer	How it is made	Chain structure
   High density polythene	Ziegler-Natta catalyst, low pressure	linear, closely packed
   Low density polythene	Traces of O₂ or peroxide, 1000 to 2000 atm, 350 to 570 K	highly branched, loosely packed
   Polytetrafluoroethene (Teflon)	CF₂=CF₂, free radical catalyst, high pressure	linear, but not made with Ziegler-Natta
   Polyacrylonitrile	CH₂=CHCN, peroxide catalyst	not polythene at all

3. So. Linear, closely packed and made with (C₂H₅)₃Al + TiCl₄ at low pressure: X is high density polythene, option (a).

The idea to keep. For polythene, remember the pairing: Ziegler-Natta at low pressure gives linear HDPE, while free radicals at very high pressure give branched LDPE.

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