Abstract
A consistent set of thermochemical property values, Δ (f) H°, Δ (f) G°, S°, and Cpo , at 298.15 K is given for the known constituents of aqueous sulfur dioxide ( SO20(aq) , HSO3-(aq) , SO32-(aq) , H(+)(aq), and S2O52-(aq) ). Also tabulated are values of the mean ionic activity coefficients, osmotic coefficients, partial pressure of SO(2)(g), and the relative apparent molar enthalpy as a function of concentration of SO(2)(aq) at 298.15 K. The data analysis considered a wide variety of measurement techniques: calorimetric enthalpies of solution and reaction, heat capacities, equilibrium constants, solubilities, and vapor pressure measurements, both partial and total, over aqueous solutions of SO(2) for the temperature range 278 to 393 K. All auxiliary data have been taken from the most recent set of CODATA values which were converted to a standard state pressure of one bar (0.1 MPa). For the process SO2(g) = SO20(aq) , the selected "best" values are: K = 1.23±0.05 mol kg(-1) bar(-1), ΔG° = -0.5±0.10 kJ mol(-1), ΔH° = -26.97±0.30 kJ mol(-1), and ΔCpo = 155 ± 10 J mol-1 K-1 . The standard state partial molar entropy of SO32-(aq) , obtained by the analysis of data via two independent thermodynamic pathways is -15.40±0.80 J mol(-1) K(-l) at 298.15 K. Parameters are given which extend the predictions to temperatures up to 373 K.