The temperature dependence of the standard-state thermodynamic properties of aqueous nonelectrolytes

Recent experimental studies of the standard-state heat capacities of aqueous nonelectrolytes at high temperatures make it possible to test predictions made with theoretical equations of state and correlation algorithms. Existing predictive methods are qualitatively correct and produce quantitative results that are in reasonable agreement with the new experimental data at temperature less than or equal to 350 degreesC, but much better results are possible using new data. Regression of the new data for CO2(aq), H2S(aq), CH4(aq), NH3(aq), and SO2(aq) leads to revised parameters for the revised Helgeson-Kirkham-Flowers (HKF) equation of state. New correlations based on these parameters allow revised regressions of older data for Xe(aq), Ar(aq), and C2H4(aq) and lead to new predictions for several other aqueous nonelectrolytes. These predictions are tested against experimentally determined equilibrium constants for reactions involving several other aqueous nonelectrolytes, including He(aq), Ne(aq), Kr(aq), Rn(aq), H-2(aq), N-2(aq), O-2(aq), and CO(aq). The correlations developed are used to make predictions for a variety of other aqueous nonelectrolytes, allowing incorporation of these species into models of geochemical processes. Copyright (C) 2001 Elsevier Science Ltd.