I have had a hard time understanding the sign of the solute and solvent particles mix (ΔHmix). Why does the third component, ΔHmix, is always exothermic (ΔHmix < 0) ?
Based on the overall enthalpy change, ΔHsoln = ΔHsolute + ΔHsolvent + ΔHmix,
I can understand why does ΔHsolute and ΔHsolvent are endothermic because separation of the solute particles from one another always requires an input of energy to overcome their attractive interactions.
Then, I thought that the third component also requires some amount of energy to make interactions between solute particles and solvent particles that is endothermic.