Thermodynamic data for the dissolution of two sparingly soluble salts, X and Y

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

Problem

Thermodynamic data for the dissolution of two sparingly soluble salts, X and Y, are listed below. Assume the listed values do not vary with temperature. Salt X: ΔHdiss∘=+22.4 kJ mol−1\Delta H^{\circ}_{\text{diss}} = +22.4\,\text{kJ}\,\text{mol}^{-1}, ΔSdiss∘=+64.0 J mol−1 K−1\Delta S^{\circ}_{\text{diss}} = +64.0\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1} Salt Y: ΔHdiss∘=−11.3 kJ mol−1\Delta H^{\circ}_{\text{diss}} = -11.3\,\text{kJ}\,\text{mol}^{-1}, ΔSdiss∘=−15.0 J mol−1 K−1\Delta S^{\circ}_{\text{diss}} = -15.0\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1} (a) For each salt, determine the standard free energy change for dissolution at 298 K and at 348 K. Express each answer to three significant figures and include appropriate units. (b) Based on your results, indicate which salt will exhibit a larger relative increase in solubility when the temperature is raised from 298 K to 348 K. Support your answer with quantitative evidence from part (a).

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