For water, Δ Hvap ≈ 41 kJ mol⁻¹. The molar entropy of vaporization at 1 atm pressure is approximately

(b) 110 J K⁻¹ mol⁻¹. Explanation: ΔSvap = 41,000/373 ≈ 110 J K⁻¹ mol⁻¹.

Q109 · 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)$410 \mathrm{J} \mathrm{K}^{-1} \mathrm{mol}^{-1}$

(b)$110 \mathrm{J} \mathrm{K}^{-1} \mathrm{mol}^{-1}$

(c)$41 \mathrm{J} \mathrm{K}^{-1} \mathrm{mol}^{-1}$

(d)$11 \mathrm{J} \mathrm{K}^{-1} \mathrm{mol}^{-1}$

Answer

Answer: B ✓ checked by 4AB · confidence high

Explanation

ΔS_vap = 41,000/373 ≈ 110 J K⁻¹ mol⁻¹.

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