The following thermodynamic data were measured for the dissolution of solid in water

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

Problem

The following thermodynamic data were measured for the dissolution of solid KNO3\text{KNO}_3 in water. ΔHdissolution=+34.9 kJ mol−1\Delta H_\text{dissolution}= +34.9\,\text{kJ}\,\text{mol}^{-1} ΔSdissolution=+109 J mol−1 K−1\Delta S_\text{dissolution}= +109\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1} Assume both quantities are nearly temperature-independent over the temperature range considered. (a) Calculate the standard free-energy change, ΔG∘\Delta G^{\circ}, for the dissolution of KNO3\text{KNO}_3 at 298 K. Include the proper sign and units. (b) On the basis of your result in part (a), determine whether the dissolution is spontaneous at 298 K. (c) Calculate the temperature (to the nearest kelvin) at which the value of ΔG∘\Delta G^{\circ} for this process is expected to change sign. State whether dissolution becomes spontaneous above or below this temperature and explain your reasoning.

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