Dissolving potassium chloride in water has and at

PHYSICS · Multi-part · Fermi University Physics · Thermal, Statistical & Complex Systems · Biophysics & Medical Physics · Physical foundations of the living cell

Life at Thermal Energy, Ch Entropy, free energy and the forces that counting produces

Problem

Dissolving potassium chloride in water has ΔH=+17.2 kJ mol−1\Delta H = +17.2\,\mathrm{kJ\,mol^{-1}} and ΔS=+76 J K−1 mol−1\Delta S = +76\,\mathrm{J\,K^{-1}\,mol^{-1}} at 298 K298\,\mathrm{K}. A student notices that the beaker feels cold as the salt dissolves and argues: "the process takes in heat rather than releasing it, so it cannot be a spontaneous process, since spontaneous processes release energy." ((a)) Calculate ΔG\Delta G for dissolving one mole of potassium chloride at 298 K298\,\mathrm{K}. ((b)) State whether the process is spontaneous, and explain what is wrong with this reasoning.

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