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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 · 2022 · Mains Paper II

Q13(b). Enthalpy of reaction when K doubles between 25 and 35 °C

Question

The equilibrium constant of the reaction X ⟶ Y is doubled when temperature is raised from 25 °C to 35 °C. Calculate the enthalpy of the reaction.

Answer in brief

ΔH° = +52.9 kJ mol⁻¹ (+12.65 kcal mol⁻¹): the reaction is endothermic.

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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 →

Coversvan ’t Hoff equationequilibrium constantenthalpy of reactiontemperature dependence of Kendothermic reaction

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