THERMODYNAMICS OF AQUEOUS ZINC - STANDARD PARTIAL MOLAR HEAT-CAPACITIES AND VOLUMES OF ZN2-DEGREES-C( (AQ) FROM 10 TO 55)

The apparent molar heat capacities and volumes of aqueous Zn(ClO4)2 ha ve been measured from 10-55-degrees-C in a Picker flow microcalorimete r and vibrating tube densimeter. The Guggenheim form of the extended D ebye-Huckel equation was fitted to the experimental data, to obtain th e following expressions for the standard-state properties from 10-55-d egrees-C: C(p)-degree(Zn(ClO4)2, aq)/JK-1 mol-1 = 3850.8 - 150720/T - 190 - 8.4956T (1) and V-degree(Zn(ClO4)2, aq)/cm3 mol-1 = 116.65 - 407 3/T - 190 - 0.050374T. (2) The standard partial molar heat capacities and volumes for Zn2+(aq) were extrapolated to higher temperatures by e mploying the Helgeson-Kirkham-Flowers (HKF) equations, amended to incl ude a standard-state correction term. Gibbs energies calculated from t he extrapolated heat capacity and volume functions are consistent with limited experimental data for the solubility of ZnO in acidic to near -neutral aqueous solutions at 200-300-degrees-C (Bourcier and Barnes, 1987).