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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

Q2. Compressibility factor and molar volume of a real gas

Question

A gas at 350 K and 12 atm has a molar volume 12 percent larger than that calculated from the perfect gas law. (a) Calculate the compressibility factor under these conditions. Which forces (attractive or repulsive) are dominating under these conditions? (b) Calculate the molar volume of the gas.

Answer in brief

(a) Z = 1.12; repulsive forces dominate. (b) Vm = 2.68 L mol⁻¹.

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Topic notes: real gases, the van der Waals equation, critical constants and Boyle temperature, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverscompressibility factorreal gasmolar volumerepulsive forcesperfect gas law