Q49 · CSIR-NET Chemistry, December 2019

Paper: CSIR-NET December 2019 · Subject: Physical Chemistry · Chapter: Statistical Thermodynamics · Topic: Statistical Thermodynamics – General · Marks: 2 · Difficulty: Medium

The molar residual entropy (in $\mathrm{J\,K^{-1}}$) of solid OCS would be closest to
(a)0
(b)2.9
(c)5.8
(d)8.7
Answer
Answer: C ✓ checked by 4AB · confidence high

The source book printed no answer; this one was worked out and checked — see the explanation.

Explanation
OCS molecules can freeze in two nearly equivalent orientations (OCS/SCO), so W = 2 per molecule and the molar residual entropy is $S = R\ln 2 = 8.314\times0.693 = 5.76 \approx 5.8\ \mathrm{J\,K^{-1}\,mol^{-1}}$. Answer: (c)

Study loop for Statistical Thermodynamics

1. Practise the PYQsPrevious-year questions, with answers

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