Solid-solute phase equilibria in aqueous solution. XII. Solubility and thermal decomposition of smithsonite
Preis, W., Königsberger, E. and Gamsjäger, H. (2000) Solid-solute phase equilibria in aqueous solution. XII. Solubility and thermal decomposition of smithsonite. Journal of Solution Chemistry, 29 (7). pp. 605-618.
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The solubility constant of ZnCO3, smithsonite, in aqueous NaClO4 solutions has been investigated as a function of temperature (288.15 ≤ T/K ≤ 338.15) at constant ionic strength I = 1.00 mol-kg-1. In addition, the solubility of zinc carbonate has been determined at 2.00 and 3.00 mol-kg-1 NaClO4 (298.15 K). The solubility measurements have been evaluated by applying the Davies approximation, the specific ion-interaction theory, and the Pitzer model, respectively. The thermodynamic interpretation leads to an internally consistent set of thermodynamic data for ZnCO3 (298.15 K): solubility constant log *K0ps0 = 7.25± 0.10, standard Gibbs energy of formation ΔfG⊖ (ZnCO3) = (-737.3±0.6) kJ-mol-1, standard enthalpy of formation ΔfH⊖(ZnCO3) = (-820.3±3.0) kJ-mol-1, and standard entropy S⊖(ZnCO3) = (77±10) J-mol-1-K-1. Furthermore, the DSC curve for the thermal decarbonation of zinc carbonate has been recorded in order to obtain the enthalpy of formation ΔfH⊖(ZnCO3) = (-820.2±2.0) from the heat of decomposition. Finally, our results are also consistent within the experimental error limits with a recent determination of the standard entropy of smithsonite, leading to a recommended set of thermodynamic properties of ZnCO3: ΔfG⊖(ZnCO3) = (-737.3±0.6) kJ-mol-1 ΔfH⊖(ZnCO3) = (-818.9±0.6) kJ-mol-1 S⊖(ZnCO3) = (81.2±0.2) J-mol-1-K-1.
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|Copyright:||2000 Plenum Publishing Corporation|
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