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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 · 2021 · Paper I

Q4(c). Clausius–Clapeyron equation

Question

Derive the Clausius–Clapeyron equation for a one-component system at equilibrium, represented as water (liquid) ⇌ water (vapour).

Answer in brief

The exact coexistence relation is dp/dT = Δ_vapH/(TΔ_vapV); for an ideal dilute vapour with negligible liquid volume, d ln p/dT = Δ_vapH/(RT²).

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Topic notes: the phase rule, phase diagrams, the Clausius–Clapeyron equation, eutectics and partially miscible liquids, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversClausius–Clapeyron equationClapeyron equationvapour pressureenthalpy of vaporisationliquid–vapour equilibrium

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