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Indian Forest Service (Mains)

Chemistry optional

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

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2024 · Paper I

Q4(c). BET surface-area measurement

Question

What is the meaning of isotherm? Write BET equation and explain how specific surface area of a solid is determined.

Answer in brief

An adsorption isotherm relates uptake to gas pressure at constant temperature. BET fitting gives the monolayer amount, which is converted to area using the molecular cross-section of the adsorbate.

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

Coversadsorption isothermBET equationspecific surface areamonolayer capacitynitrogen adsorption 77 K

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