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

Abstract

The EMF data of different metal chlorides (2:1 electrolytes) were obtained by using a cell [M X Hg|MCl 2 ( m)|AgCl–Ag] at two temperatures. Stock solutions of metal chlorides (CoCl 2, CuCl 2 and ZnCl 2) 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°) values of the above cell were calculated from the measured EMF of these mixtures. The standard thermodynamic functions (Δ G°, Δ H° and Δ S°) and respective transfer parameters of MCl 2 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 ( α 1 and α 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 ( γ ±) of electrolytes.