Thermodynamics of aqueous zinc: Standard partial molar heat capacities and volumes of Zn 2+(aq) from 10 to 55°C

Abstract

The apparent molar heat capacities and volumes of aqueous Zn(ClO 4) 2 have been measured from 10–55°C in a Picker flow microcalorimeter and vibrating tube densimeter. The Guggenheim form of the extended Debye-Hückel equation was fitted to the experimental data, to obtain the following expressions for the standard-state properties from 10–55°C: C p 0(Zn(ClO 4) 2, aq)/JK −1 mol −1 = 3850.8 − 150720 T−190 − 8.4956T (1) and V 0(Zn(ClO 4) 2, aq)/cm 3 mol −1 = 116.65 − 4073 T−190 − 0.050374T . (2) The standard partial molar heat capacities and volumes for Zn 2+(aq) were extrapolated to higher temperatures by employing the Helgeson-Kirkham-Flowers (HKF) equations, amended to include a standardstate correction term. Gibbs energies calculated from the 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°C ( bourcier and barnes, 1987).