One mole of argon gas and one mole of liquid water are each heated from 298 K to 373…

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

One mole of argon gas and one mole of liquid water are each heated from 298 K to 373 K at constant pressure. Over this temperature interval the molar heat capacities may be taken as temperature-independent: Cp,m(Ar)=20.8 J mol−1 K−1C_{p,m}(\text{Ar}) = 20.8\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1} Cp,m(H2O, liq)=75.3 J mol−1 K−1C_{p,m}(\text{H}_2\text{O, liq}) = 75.3\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1}. (a) Calculate the molar entropy change, ΔSm\Delta S_m, for heating the argon gas from 298 K to 373 K. (b) Calculate the molar entropy change, ΔSm\Delta S_m, for heating the liquid water over the same temperature range. (c) Despite the larger heat capacity of liquid water, the entropy change you obtained in part (b) may be smaller than or comparable to that in part (a). Use molecular-level reasoning to explain why.

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