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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 · 2019 · Mains Paper II

Q13(a). Pressure dependence of mole-fraction equilibrium

Question

For ammonia formation, explain why pressure affects Kₓ but not Kₚ at constant temperature, deriving their relation for ideal gases. The paper prints N₂ + 3H₂ ⇌ 3NH₃.

Answer in brief

The balanced reaction is N₂ + 3H₂ ⇌ 2NH₃. For it, Kₚ=Kₓ(p/p°)⁻², so Kₓ=Kₚ(p/p°)².

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CoversPressure dependence of mole-fraction equilibriumChemical equilibrium

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