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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 I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2022 · Paper I

Q8(c). Stationary and branching chain reactions; conditions for explosion

Question

Define stationary and non-stationary (branching) chain reaction. Non-stationary chain reactions always lead to explosion under certain conditions. Give a detailed account of these conditions.

Answer in brief

Stationary chain: each propagation step uses one carrier and makes one, so carriers reach a steady number; branching chain: some steps make two or more carriers from one; explosion occurs when branching outruns termination (f > g) or heat is produced faster than lost.

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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: Arrhenius equation, collision theory and transition-state theory, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverschain reactionbranching chainexplosion limitshydrogen–oxygen reactionthermal explosionchain carriers

All parts of Question 8