(Solid + solute) phase equilibria in aqueous solution. XIII. Thermodynamic properties of hydrozincite and predominance diagrams for (Zn2 + + H2O + CO2) |
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| Affiliation: | 1. CHU de Bordeaux, Service de Médecine Nucléaire, F-33604 Pessac, France;2. Université de Bordeaux 2, Centre de Recherche Cardio-Thoracique, F-33076 Bordeaux, France;3. INSERM U 1045, Centre de Recherche Cardio-Thoracique, F-33076 Bordeaux, France;1. Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia;2. Department of Earth Science and Engineering, Imperial College London, South Kensington, SW7 2AZ, UK;3. Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK;4. International Research Centre "Smart Materials", Southern Federal University, Sorge 5, Rostov-on-Don 344090, Russia;5. Plymouth Electron Microscopy Centre, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK;6. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK;7. Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK |
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| Abstract: | ![]()
The thermodynamic properties ofZn5(OH)6(CO3)2 , hydrozincite, have been determined by performing solubility and d.s.c. measurements. The solubility constant in aqueous NaClO4media has been measured at temperatures ranging from 288.15 K to 338.15 K at constant ionic strength (I = 1.00 mol · kg − 1). Additionally, the dependence of the solubility constant on the ionic strength has been investigated up to I = 3.00 mol · kg − 1NaClO4at T = 298.15 K. The standard molar heat capacity Cp, mofunction fromT = 318.15 K to T = 418.15 K, as well as the heat of decomposition of hydrozincite, have been obtained from d.s.c. measurements. All experimental results have been simultaneously evaluated by means of the optimization routine of ChemSage yielding an internally consistent set of thermodynamic data (T = 298.15 K): solubility constant log * Kps 00 = (9.0 ± 0.1), standard molar Gibbs energy of formationΔfGmo {Zn5(OH)6(CO3)2 } = ( − 3164.6 ± 3.0)kJ · mol − 1, standard molar enthalpy of formation ΔfHmo{Zn5(OH)6(CO3)2 } = ( − 3584 ± 15)kJ · mol − 1, standard molar entropy Smo{Zn5(OH)6(CO3)2 } = (436 ± 50)J · mol − 1· K − 1and Cp,mo / (J · mol − 1· K − 1) = (119 ± 11) + (0.834 ± 0.033)T / K. A three-dimensional predominance diagram is introduced which allows a comprehensive thermodynamic interpretation of phase relations in(Zn2 + + H2O + CO2) . The axes of this phase diagram correspond to the potential quantities: temperature, partial pressure of carbon dioxide and pH of the aqueous solution. Moreover, it is shown how the stoichiometric composition{n(CO3) / n(Zn)} of the solid compoundsZnCO3 and Zn5(OH)6(CO3)2can be checked by thermodynamically analysing the measured solubility data. |
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