Calculation of the standard partial molal thermodynamic properties and dissociation constants of aqueous HCl 0 and HBr 0 at temperatures to 1000°C and pressures to 5 kbar

Abstract

Dissociation constants of aqueous ion pairs HCl 0 and HBr 0 derived in the literature from vapor pressure and supercritical conductance measurements (Quist and Marshall, 1968b; Frantz and Marshall, 1984) were used to calculate the standard partial molal thermodynamic properties of the species at 25°C and 1 bar. Regression of the data with the aid of revised Helgeson-Kirkham-Flowers equations of state (Helgeson et al., 1981; Tanger and Helgeson, 1988; Shock et al., 1989) resulted in a set of equations-of-state parameters that permits accurate calculation of the thermodynamic properties of the species at high temperatures and pressures. These properties and parameters reproduce generally within 0.1 log unit (with observed maximum deviation of 0.23 log unit) the log K values for HBr 0 and HCl 0 given by Quist and Marshall (1968b) and Frantz and Marshall (1984), respectively, at temperatures to 800°C and pressures to 5 kbar.