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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper II covers organic chemistry and spectroscopy.

UPSC Civil Services (Mains), Chemistry optional · 2024 · Paper II

Q6(a)(ii). Atactic, syndiotactic and isotactic polystyrene

Question

Predict the physical properties of atactic, syndiotactic and isotactic polystyrenes based on their structure.

Answer in brief

Regular placement of phenyl groups allows crystallisation: iso- and syndiotactic polystyrene are crystalline and high-melting; atactic is amorphous.

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The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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Topic notes: polymers: polymerisation, Ziegler–Natta and molar mass, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverstacticitypolystyreneisotacticsyndiotacticatacticcrystallinity

All parts of Question 6