A solution is made by dissolving solute B in solvent A. Consider the A-A attractive forces, the B-B attractive forces, and the A-B attractive forces.

Question

If the solution process is exothermic, what can you say about the relationships between these attractive forces?

Answer 1

If the solution process is exothermic, that means that heat is given off (liberated) during the process. Since the solution process consists of ...

breaking A-A bonds, breaking B-B bonds and forming A-B attractive forces.

Breaking bonds (A-A and B-B) requires energy so in endothermic and making bonds (A-B forces) releases or liberates energy (exothermic), the sum of breaking A-A and B-B bonds must be less than the energy of forming A-B attractive forces.

Put another way, the energy needed to break the solute and solvent bonds, is less than the energy released by surrounding the solute ions or molecules with solvent ions or molecules.