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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 · 2023 · Paper I

Q4(b). Chemical potential versus temperature

Question

(i) Show that the slope of μ versus T curve for a pure substance (existing in three phases—solid, liquid and gas) is always negative and is equal to −Sₘ. (ii) Draw a schematic diagram and show that (∂μₛ/∂T)P > (∂μₗ/∂T)P ≫ (∂μ_g/∂T)P. Locate the melting point and boiling point. (5+5 marks)

Answer in brief

At fixed pressure, dμ/dT = −Sₘ. Gas has the most negative slope. The stable phase follows the lowest chemical-potential curve, switching at the melting and boiling intersections.

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Coverschemical potentialμ versus T diagramphase stabilitymelting pointboiling pointmolar entropy

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