Thermodynamic Functions from Mayer's Theory of Ionic Solutions. I. Equations for Thermodynamic Functions

Abstract

For an ionic solute, Mayer has previously derived from statistical mechanics an analytical expression for a mean activity coefficient which, however, is not usually measured. From the partial molal free energy expression defining Mayer's activity coefficient, there are derived in this paper expressions for five usually measured thermodynamic functions. These are the change in partial molal volume with concentration; the change in apparent molal volume with concentration; the relative partial molal heat content; the relative apparent molal heat content; and the stoichiometric mean ionic molar activity coefficient. Formulas for these five functions involve the coefficients of thermal expansion and isothermal compressibility of the solution and solvent; the solvent dielectric constant and its pressure and temperature derivatives; and readily computable analytic expressions arising from the theory.