Determination of energy change associated with dissolution of a solid

The dissolution of a solid immersed in a solvent was considered as a consecutive process, consisting of a primary surface interaction leading to the production of a new surface at the solid-liquid interface, solvation of the solid at the interface, and transfer of the solvated solid into the bulk of the solution. The energy changes involved in each step were studied for the dissolution of m-tolylacetamide in hexane and heptane. An energy diagram was constructed according to the proposed dissolution mechanism. The heats of dissolution determined from the energy diagram agreed well with those obtained experimentally.