That is, when a gas dissolves in a liquid solvent, energy is released as heat, warming both the system (i.e. the solution) and the surroundings.
The temperature of the solution eventually decreases to match that of the surroundings.
The energy released by the solvation of the ammonium ions and nitrate ions is less than the energy absorbed in breaking up the ammonium nitrate ionic lattice and the attractions between water molecules.
Dissolving potassium hydroxide is exothermic, as more energy is released during solvation than is used in breaking up the solute and solvent.
The expressions of the enthalpy change of dissolution can be differential or integral, as a function of the ratio of amounts of solute-solvent.
is the infinitesimal variation, or differential, of the mole number of the solute during dissolution.
The integral heat of dissolution is defined as a process of obtaining a certain amount of solution with a final concentration.
The enthalpy change in this process, normalized by the mole number of solute, is evaluated as the molar integral heat of dissolution.