Thermodynamics of Strong Aqueous Electrolyte Solutions at t = 25 °C Described by the Hückel Equations

Abstract

A theoretical framework based on the Hückel equation for activity coefficients has been developed, and the physicochemical properties of 57 binary strong electrolyte solutions at t = 25 °C have been correlated. These properties include the activity and osmotic coefficients, apparent molar relative enthalpies, apparent molar heat capacities, and apparent molar volumes. The correlating equations agree well with property values from the literature up to concentrations of m = 2.0 mol kg–1 for 1:1 electrolytes and m = 0.5 mol kg–1 for 2:1, 1:2, and 3:1 electrolytes. Certain electrolytes could not be satisfactorily represented, including polyprotic acids, 2:2 electrolytes, and the zinc and cadmium halides. In addition to quantifying Hückel equation parameters that can be used for the convenient calculation of physicochemical property values, the results provide a benchmark against which other theoretical frameworks with few adjustable parameters can be compared.