Potassium nitrate, KNO3, dissolves in water with a standard molar enthalpy change of +35.7kJmol−1 and a standard molar entropy change of +118Jmol−1K−1.
Assume that these thermodynamic quantities remain constant over the temperature range considered.
(a) Calculate the temperature, in kelvins, at which the dissolution of KNO3 changes from being non-spontaneous to spontaneous under standard-state conditions.
(b) Using your calculation, predict whether the solubility of KNO3 in water will increase, decrease, or remain essentially unchanged when the temperature is raised from 298 K to 373 K. Provide a brief justification.