Q34 · CSIR-NET Chemistry, December 2012

Paper: CSIR-NET December 2012 · Subject: Physical Chemistry · Chapter: Thermodynamics · Topic: Laws State Functions · Marks: 2 · Difficulty: Medium

For water, $\Delta \mathrm{H}_{\text {vap }} \approx 41 \mathrm{kJ} \mathrm{mol}^{-1}$. The molar entropy of vaporization at 1 atm pressure is approximately
(a)$410\,\mathrm{J\,K^{-1}\,mol^{-1}}$
(b)$110\,\mathrm{J\,K^{-1}\,mol^{-1}}$
(c)$41 \mathrm{J} \mathrm{K}^{-1} \mathrm{mol}^{-1}$
(d)$11\,\mathrm{J\,K^{-1}\,mol^{-1}}$
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
ΔS_vap = ΔH_vap/T_b = 41000/373 ≈ 110 J K⁻¹ mol⁻¹ (Trouton-like value).

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