Nonideal gas solvation thermodynamics.

General expressions are obtained for the thermodynamic properties of nonideal gases of arbitrary composition. These include the equation of state and solvation thermodynamic functions of mixtures with any number of components, expanded to first order in total number density. The results are expressed in terms of binary second virial coefficients which are in turn related to binary interaction potential energy functions. Solvation thermodynamic functions (at both constant pressure and constant volume) are decomposed into solute-solvent and solvent-reorganization contributions, thus indicating how each of the latter quantities may be experimentally measured. Moreover, the results are used to identify solute-induced changes in solvent thermodynamic functions, as well as nonideal (excess) contributions to chemical reaction equilibria and solvation heat capacities. The effects of a solute on the reorganization energy and chemical potential of a nonideal solvent are shown to differ qualitatively from both the corresponding ideal gas and high density fluid results.