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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 · 2020 · Mains Paper II

Q2. Comparing van der Waals gases

Question

For gases A, B, C and D, the SI values of a are 0.6, 0.6, 0.2 and 0.005, while the tabulated values of 10³b are 0.025, 0.15, 0.10 and 0.02. Identify: (i) highest critical temperature; (ii) greatest molecular volume; (iii) highest Tᵣ/pᵣ at 273 K and 1 atm; (iv) most nearly ideal gas there. Explain.

Answer in brief

(i) A; (ii) B; (iii) D; (iv) C is closest in compressibility factor at the stated conditions; D has the smallest separate interaction corrections.

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CoversComparing van der Waals gasesReal gases