The heat of solution is the heat that is absorbed when one substance dissolves in another to formation a homogeneous mixture. A homogeneous mixture is one which a sample of the mixture that contains a substantial number of molecules has the same composition as any other sample: the components of the mixture are distributed uniformly throughout. In common usage, the heat of solution is used in place of the more precise term the enthalpy of solution, which has the symbol ()H_soln. The enthalpy of solution is the heat of solution for dissolution of one mole of a substance in another substance such that the final solution is one molar and three conditions are fulfilled: (1) the pressure remains constant, (2) the only possible work that occurs is expansion against the atmosphere (so-called P()V work) and (3) the temperature remains constant during the process. The enthalpy...