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UPSC Combined Geo-Scientist

Chemist

  • 2 objective papers
  • 120 questions each
  • 2 h per paper
  • 100 + 300 marks

Prelims Paper II covers chemistry.

UPSC Combined Geo-Scientist, Prelims · 2020 · Paper II, Chemistry · Q55 of 120

Geo-Scientist Prelims 2020 Chemistry Q55: The entropy of vaporization of a liquid is 100 J mol⁻¹K⁻¹ and it…

QuestionThermodynamics / Trouton-type relation

The entropy of vaporization of a liquid is 100 J mol⁻¹K⁻¹ and it boils at 300K. What would be the value of ∆Hvap?

  1. (a) 3.0 kJ mol⁻¹
  2. (b) 30.0 kJ mol⁻¹
  3. (c) 300 kJ mol⁻¹
  4. (d) 3000 kJ mol⁻¹

Answer: (b) 30.0 kJ mol⁻¹

At boiling point, ΔSvap = ΔHvap/Tb → ΔHvap = 100 × 300 = 30,000 J mol⁻¹ = 30.0 kJ mol⁻¹ → (b).

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