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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(e). Langmuir isotherm and the kinetics of surface reactions

Question

Derive Langmuir adsorption isotherm. How does Langmuir adsorption isotherm help in elucidation of kinetics of a gaseous reaction on solid surface?

Answer in brief

θ = KP/(1 + KP), K = ka/kd; a surface reaction goes at a rate proportional to the coverage, so the isotherm turns the rate into a function of pressure, e.g. rate = kKP/(1 + KP).

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Topic notes: adsorption isotherms, heterogeneous catalysis and colloids, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversLangmuir adsorption isothermsurface coverageheterogeneous catalysisLangmuir–Hinshelwood mechanismzero-order kinetics

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