(Solid + solute) phase equilibria in aqueous solution. XIII. Thermodynamic properties of hydrozincite and predominance diagrams for (Zn2++ H2O+ CO2) (original) (raw)

The thermodynamic properties of the copper carbonates malachite, Cu 2 (OH) 2 CO 3 , and azurite, Cu 3 (OH) 2 (CO 3 ) 2 , have been obtained from solubility measurements as a function of temperature as well as ionic strength of aqueous perchlorate media. First, solubility constants have been determined from T = 288.15 K to T = 338.15 K at constant ionic strength, I = 1.00 mol · kg −1 NaClO 4 . Second, solubility experiments have been carried out from I = 1.00 mol · kg −1 to I = 3.00 mol · kg −1 NaClO 4 at constant temperature, T = 298.15 K. All experimental data have been evaluated by application of the optimization routine of ChemSage, yielding an internally consistent set of thermodynamic properties for malachite (T = 298.15 K): log K 0 ps0 (mal.) = (6.34 ± 0.10), f G o m {Cu 2 (OH) 2 CO 3 } = (−903.3 ± 1.2) kJ · mol −1 , f H o m {Cu 2 (OH) 2 CO 3 } = (−1067.1 ± 3.4) kJ · mol −1 , S o m {Cu 2 (OH) 2 CO 3 } = (166.3 ± 2.5) J · mol −1 · K −1 ; and azurite (T = 298.15 K): log K 0 ps0 (azu.) = (6.30 ± 0.10), f G o m {Cu 3