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Geochimica et Cosmochimica Acta

The solubility of strontianite (SrCOthree) in CO2-HtwoO solutions between ii and 91°C, the association constants of SrHCO+ 3(aq) and SrCO0 3(aq) between five and eighty°C, and an evaluation of the thermodynamic backdrop of Srii+(aq) and SrCOthree(cr) at 25°C and 1 atm total force per unit area

Abstract

Lxx new measurements (SrT-Pco2 of the solubility of strontianite were used to evaluate the equilibrium constant for the reaction SrCO 3(cr) = Sr 2+(aq) + CO two− three(aq) between 2 and 91 °C. The temperature dependence of the equilibrium constant is given past the expression Log 1000 = 155.0305 − 7239.594/T − 56.58638 log T where T is in degrees Kelvin. The log One thousand of strontianite, the Gibbs energy, enthalpy and entropy of the reaction at 25°C are −9.271 ± 0.020, 52.919 ± 0.08 kJ · mol−1, −1.67 ± 1.30 kJ · mol−ane, and −183.1 ± iv.0 J · mol−1 · Chiliad −ane, respectively. The equilibrium constants are consistent with an aqueous model that includes the ion pairs SrHCO+ 3(aq) and SrCO0 3(aq) which were evaluated by potentiometric methods betwixt 5 and 80°C. The equilibrium constant for the association reaction Sr 2+(aq) + HCO − 3(aq) = SrHCO + 3 aq) is given by the expression Log K SrHCO + three = −3.248 + 0.014867T. The log of the association constant, the Gibbs energy, enthalpy and entropy of the reaction at 25°C are 1.18, −vi.76 kJ · mol−i, 25.thirty kJ · mol−1, and 107.5 J · mol−1 · K−1, respectively. The equilibrium abiding for the association reaction Sr two+(aq) + CO two− 3(aq) = SrCO 0 3 aq) is given past the expression Log K SrCO 0 3 = −1.019 + 0.012826T. The log of the association constant, the Gibbs energy, enthalpy, and entropy of the reaction at 25°C are 2.81, −16.01 kJ · mol−1,21.83 kJ · mol−1, and 126.9 J · mol−1 · Thou−1, respectively. These results atomic number 82 to reliable calculation of the aqueous speciation and solubility of strontianite in the arrangement SrCOthree-CO2-H2O from 0 to more than 90°C. Literature data on the solubility of strontianite have been evaluated and compared with these results.

Our new data for strontianite have been used in an evaluation of the thermodynamic properties of Sr2+(aq), SrCO3(cr) and related compounds. The following values are recommended for the standard enthalpy (kJ · mol−one), Gibbs energy (kJ · mol−1), and entropy (J · mol−one · K−i), respectively, of Sr2+aq): −550.90 ± 0.fifty, −563.83 ± 0.8 and −31.50 ± ii.0, and for SrCO3(cr): −1225.77 ± i.1, −1144.73 ± one.0 and 97.2.

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