For ideal solutions, the integral heat of solution is exactly zero. Ideal solutions are characterized by the absence of intermolecular interactions between the solute and solvent molecules and perfect mixing at the molecular level. In such cases, no heat is released or absorbed during the dissolution process, as the solute molecules are distributed uniformly throughout the solvent without any changes in their energy states.
In contrast, the heat of the mixing is never zero for real solutions due to the interactions between solute-solvent molecules, solvation process involved, or some chemical reactions between components taking place in the solution.
