A unified approach for prediction of thermodynamic properties of aqueous mixed-electrolyte solutions. Part I: vapor pressure and heat of vaporization

Abstract

The overall nonideality of an aqueous mixed electrolyte solution is characterized in terms of a newly defined parameter Γ^*, called the overall reduced ionic activity coefficient. It is shown that Γ^* for the mixed solution is simply related to the properties of single-electrolyte solutions. Γ^* is related to the vapor pressure of a mixed-electrolyte solution through well-known thermodynamic equations. This leads to a predictive equation for the vapor pressure of a mixed-electrolyte solution in terms of the vapor pressures of single-electrolyte solutions of the components. This equation is valid over the entire concentration range encountered in practice, without any empirical constants, and has a predictive accuracy of 2%. A predictive equation for the latent heat of vaporization is also developed and tested against experimental data.