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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 · 2025 · Mains Paper II

Q11(b). Kc from Kp for the dissociation of ammonia

Question

The value of Kp for the reaction NH₃(g) ⇌ ½N₂(g) + 3/2H₂(g) (at 298 K) is 1.36 × 10⁻³. Determine the corresponding value of its Kc.

Answer in brief

Kc = 5.56 × 10⁻⁵ mol L⁻¹ (pressures in atm).

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Topic notes: chemical equilibrium, ΔG° = −RT ln K, Kp, Kc, Kx and the van ’t Hoff equations, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversKp and Kc relationKp = Kc(RT)^Δnequilibrium constantammonia dissociationΔn

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