Thermodynamic determination of solvation potentials of various metal chlorides by (1,4-dioxane + water) mixtures through EMF measurements

The EMF data of different metal chlorides (2:1 electrolytes) were obtained by using a cell [M-X Hg]MCl2 (m)[AgCl-Ag] at two temperatures. Stock solutions of metal chlorides (CoCl2, CuCl2 and ZnCl2) were prepared by weight in 1,4-dioxane-aqueous mixtures. There was a significant change in the EMF values with change of metal chloride, its concentration and solvents composition. The standard electrode potential (E degrees) values of the above cell were calculated from the measured EMF of these mixtures. The standard thermodynamic functions (Delta G degrees, Delta H degrees and Delta S degrees) and respective transfer parameters Of MCl2 from water to 20, 45 and 70% dioxane-water mixtures were also evaluated. Equilibrium dissociation constants (K-1 and K-2) as well as the degrees of dissociation (alpha(1) and alpha(2)) were obtained by iterative procedures. The data were analyzed in terms of solute-solvent interactions depending on standard and transfer thermodynamic parameters and mean activity coefficients (gamma(+/-)) of electrolytes. (C) 2009 Elsevier B.V. All rights reserved.