The solubility of BaCO 3 (cr) (witherite) in CO 2 -H 2 O solutions between 0 and 90°C, evaluation of the association constants of BaHCO 3 + (aq) and BaCO 3 0 (aq) between 5 and 80°C, and a preliminary evaluation of the thermodynamic properties of Ba 2+ (aq

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One hundred and fifty new measurements of the solubility of witherite were used to evaluate the equilibrium constant of the reaction BaCO 3 ( cr ) = Ba 2+ ( aq ) + CO 3 2- ( aq ) between 0 and 90°C and 1 atm total pressure. The temperature dependence of the equilibrium constant is given by log K = 607.642 + 0.121098 T - 20011.25/ T - 236.4948 log T where T is in degrees Kelvin. The log K of BaCO 3 (cr), the Gibbs energy, the enthalpy and entropy of the reaction at 298.15 K are -8.562, 48.87 kJ · mol -1 , 2.94 kJ · mol -1 and -154.0 J · mol -1 · K -1 , respectively. The equilibrium constants are consistent with an aqueous model that includes the ion pairs BaHCO 3 + (aq) and BaCO 3 0 (aq) Three different methods were used to evaluate the association constant of BaHCO 3 + (aq), and all yielded similar results. The temperature dependence of the association constant for the reaction Ba 2+ ( aq ) + HCO 3 - ( aq ) = BaHCO 3 + ( aq ) is given by log K BaHCO 3 + = -3.0938 + 0.013669 T . The log of the association constant, the Gibbs energy, the enthalpy and entropy of the reaction at 298.15°K are 0.982, -5.606 kJ · mol -1 , 23.26 kJ · mol -1 and 96.8 J · mol -1 · K -1 , respectively. The temperature dependence of the equilibrium constant for the reaction Ba 2+ ( aq ) + CO 2- 3 ( aq ) = BaCO 0 3 ( aq ) is given by log K BaCO 3 0 = 0.113 + 0.008721 T . The log of the association constant, the Gibbs energy, the enthalpy and entropy of the reaction at 298.15° K are 2.71, -15.49 kJ · mol -1 , 14.84 kJ · mol -1 and 101.7 J· mol -1 · K -1 . The above model leads to reliable calculations of the aqueous speciation and solubility of witherite in the system BaCO 3 -CO 2 -H 2 O from 0 to more than 90°C. Literature data on witherite solubility were re-evaluated and compared with the results of this study. Problems in the thennodynamic selections of Ba compounds are considered. Newer data require the revision of f H° and f G° of Ba 2+ (aq) to -532.5 and -555.36 kJ · mol -1 , respectively, for agreement with solubility data.

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The solubility of BaCO 3 (cr) (witherite) in CO 2 -H 2 O solutions between 0 and 90°C, evaluation of the association constants of BaHCO 3 + (aq) and BaCO 3 0 (aq) between 5 and 80°C, and a preliminary evaluation of the thermodynamic properties of Ba 2+ (aq does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

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