Ion-Solvation Behavior of Pyridinium Dichromate in Water–N,N-Dimethyl Formamide Solvent Mixtures

Abstract

The electrical conductances of pyridinium dichromate have been measured in N,N-dimethyl formamide–water mixtures of different compositions in the temperature range 283–313 K. The limiting molar conductance, Λ0, association constant of the ion pair, KA, and dissociation constant KC have been calculated using the Shedlovsky and Kraus–Bray equations. The effective ionic radii (ri) of C5H5NH+ and \(\mathrm{Cr}_{2}\mathrm{O}_{7}^{ -}\) have been determined from the \(\Lambda_{i}^{0}\) values using Gill’s modification of Stokes’ law. The influence of the mixed solvent composition on the solvation of ions is discussed with the help of the ‘R’-factor (\(R = \frac{\eta \Lambda_{ \pm}^{0}(\mathrm{solvent})}{\eta\Lambda_{ \pm}^{0}(\mathrm{water})}\)). Thermodynamic parameters are evaluated and reported. The results of this study are interpreted in terms of ion–solvent interactions and solvent properties.