Enthalpies of dilution of aqueous solutions of HCl, MgCl2, CaCl2, and BaCl2 at 300, 325, and 350 degrees C

摘要

Dilution enthalpies, measured using isothermal dow calorimetry. are reported for aqueous solutions of BaCl2 at 300 degreesC and 11.0 MPa, MgCl2, CaCl2, and BaCl2 at 325 degreesC and 14.8 MPa, and at 350 degreesC and 17.6 MPa. Previously collected dilution enthalpies for aqueous solutions of MgCl2 and CaCl2 at 300 degreesC and 10.3 MPa and for aqueous solutions of HCl at 250, 275, and 300 degreesC at 10.3 MPa and 320 degreesC at 12.8 MPa were included with the new data at 300 degreesC and 11.0 MPa and at 350 degreesC and 17.6 MPa when fitting the Fitter parameters. The concentration range of the chloride solutions was 0.5 to 0.02 molal. Parameters for the Pitzer excess Gibbs ion-interaction equation were determined from the fits of the experimental heat data. Equilibrium constants, enthalpy changes, entropy changes, and heat-capacity changes for the association of alkaline earth metal ions and H+ with chloride ion were estimated from the heat data. For all systems, the enthalpy and entropy changes are positive and show accelerating increases with temperature. The resulting equilibrium constants show significant, but smaller, increases with temperature. [References: 35]