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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper II covers physical chemistry.

UPSC Combined Geo-Scientist, Mains · 2023 · Mains Paper II

Q10(a). Photosensitisation and how it differs from catalysis

Question

Explain the process of photosensitization with at least two examples. How does it differ from catalysis?

Answer in brief

A light-absorbing sensitiser passes its excitation energy to a molecule that cannot absorb that light, which then reacts. Unlike a catalyst, the sensitiser supplies energy.

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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: photochemistry (quantum yield, Jablonski diagram, H₂–halogen reactions), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversphotosensitisationphotosensitisermercury photosensitisationphotosynthesiscatalysis

All parts of Question 10