Conductance Determination of the Ion Association of Tris-(ethylenediamine)chromium(III) Chloride in Dimethyl Sulfoxide-Water Mixtures at Various Temperatures

Abstract

The electrical conductances of tris-(ethylenediamine)chromium chloride, ([Cr(en)(3)]Cl-3; en = ethylenediamine) were measured as functions of temperature and concentration in 20-80 wt% dimethyl sulfoxide (DMSO)-water mixtures. Conductance data were analyzed by the Kraus-Bray and Shedlovsky models. Also, density and viscosity values for 20-80 wt% DMSO-water mixtures have been determined experimentally at temperatures varying from (288.15 to 318.15) K. The limiting molar conductance, I > (0), and the association constant, K (A), for ([Cr(en)(3)]Cl-3 were computed by using Shedlovsky's equation. The I > (0) values decrease with increase in the percentage of DMSO in the mixed solvent. The K (A) values increase with increasing temperature and increasing percentage of DMSO in the mixed solvent at all temperatures. This may be attributed to the increase in association constant with the decrease in the relative permittivity of the mixed solvent. Thermodynamic parameters (Gibbs energy, enthalpy and entropy changes) were determined from the temperature dependence of K (A) for ([Cr(en)(3)]Cl-3. The results of the study have been interpreted in terms of ion-solvent interactions and solvent properties.