Determination of thermodynamic data for modeling corrosion

The aqueous reactions, H+ + Cl- = HCl, H+ + Ac- = HAc, and Na+ + Ac- = NaAc (Ac = C2H3O2-), were studied as a function of ionic strength at 275, 300, and 320 degree C using a flow calorimetric procedure. Log K, ΔH, and ΔS were determined from the fits of the calculated and experimental heats while ΔCp values were calculated from the variation of ΔH values with temperature. The log K and ΔH values for the first two reactions agree well with literature values at these temperatures. No previous results have been reported for the third reaction. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was applied to the log K values determined in this study. The resulting plots of log K for the isocoulombic reactions vs 1/T were approximately linear, which demonstrates that the ΔCp values for these reactions are approximately zero. 65 refs., 20 figs., 8 tabs