Why is the dissolution of sodium hydroxide exothermic?
The enthalpy of a solution is determined by the strengths of the intermolecular interactions between solute and solvent. When an exothermic solution forms, the strength of the interactions between the solvent and solute particles is stronger than the strength of the interactions between the solvent itself and the solute itself. When a solution forms endothermically, the interactions between solute and solvent are weaker than the interactions between either solvent or solute independent of the other. When the enthalpy of the solution is zero, the interactions between solute and solvent are equal to the interactions between the solvent itself and the solute itself. This is called an ideal solution and both the solvent and the solute will obey Raoult’s law.
