Ion-solvent interactions - studies on the solvation of electrolytes in mixed solvents

Abstract

In order to throw light on ion-solvent interactions, the solvation numbers of electrolytes in different mixed solvents (methanol + water and ethanol + water mixtures) have been determined using ultrasonic interferometer. The anomalies in the solvation number of cations (in aqueous solutions) like K +, Na + and H + are presented. The changes in the solvation numbers of electrolytes with increasing quantities of alcohol indicates some interesting features and are explained on the basis of: (i) decrease in the solvent molecules. (ii) structural re-arrangement. (iii) preferential solvation of cations and anions. (iv) Approximations in the determination of solvation numbers. The role of the solvents could hardly be explained in absence of a complete knowledge of the nature of solvation of electrolytes and particularly of ions. The subject has attracted considerable attention and the solvation number has been determined using different well-known techniques[1-4]. In order to throw light on the ion-solvent interactions, we tried to determine the solvation numbers of different known electrolytes like HCl, NaCl and KCl in water, methanol + water and ethanol + water mixtures by the compressibility method using ultrasonic interferometer. The results are presented in this communication.