Physico-chemical studies in non-aqueous solvents. X. Conductance and solvation studies of 1 : 1 electrolytes in N,N-dimethylacetamide

Abstract

Conductances of some 1 : 1 electrolytes have been measured in the concentration range 1-120 x 10^-4 mol l^-1 in N,N-dimethylacetamide at 25°. The conductance data have been analysed by Fuoss-Onsager-Skinner equations for dissociated and associated electrolytes, and limiting equivalent conductances, ion-size parameter and association constants (where appropriate) for various electrolytes have been obtained. The ion-size parameter (3.7 ± 0.3Ǻ) has been found to be about the same for all the electrolytes. Alkali metal salts are fully dissociated while the substituted ammonium salts are slightly associated in this solvent. The ionic association increases with increase in the size of cations. Transference numbers of lithium chloride, potassium thiocyanate and silver perchlorate have also been measured in the concentration range 1.1-18.4 x 10^-2mol l^-1 in this solvent. Limiting cation transference numbers are determined from the linear plots of cation transference numbers against square root of concentration. Ionic mobilities, effective ionic radii and solvation numbers of various ions in solution have been calculated. Higher solvation numbers of cations than those of anions of comparable sizes are consistent with the aprotic nature of the solvent.