What is the entropy change when 3.6 g of liquid water is completely converted into vapours at 373 K? — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Moles of water $n = 3.6\text{ g} / 18\text{ g/mol} = 0.2\text{ mol}$. Total heat $Q = n \Delta H_{vap} = 0.2 \times 40850\text{ J} = 8170\text{ J}$. $\Delta S = Q / T = 8170 / 373 = 21.90\text{ J/K}$. The closest given option is 21.89 J/K.