Conductance studies of alkali iodides in mixed organic solvents II: Conductance measurements in N, N-dimethylformamide-ethanol mixed solvents

Abstract

<span style="font-size:16.0pt;mso-bidi-font-size:12.0pt" lang="EN-IN">Limiting ionic conductivities for Na⁺, K⁺ and Cs⁺ ions have been obtained at <span style="mso-bidi-font-style:italic">25ºC<i> </i>in mixtures of ethanol and N, N-dimethylformamide over the entire solvent composition range and in the pure solvents. Variations in limiting ionic conductivities for the ions have been observed as the mole fraction of ethanol in the mixed solvents varied. These variations show a maximum at the solvent composition of near 0.8 mole fraction of ethanol in the mixed solvents for the three ions. Using Nightingale's modification of the Robin son-Stokes treatment, the radii of the solvated ions in the various solvent systems have been calculated and the solvation numbers of Na⁺, K⁺ and Cs⁺ in the various solvents calculated there from. The solvation numbers of Na⁺, K⁺ and Cs⁺ range between 2.37-3.28, 2.23-2.73 and 1.89-2.43 respectively in the various solvent mixtures. Plots of the solvation numbers as a function of solvent composition show a minimum at about 0.80 ethanol mole fraction which coincides with the maximum in the limiting ionic conductivities. The results of the study suggest that ion-solvent interactions which account for the extent of salvation of the ions is the dominant factor which influences the conductance behaviour of Na⁺, K⁺ and Cs⁺ ions in N,N-dimethyl formamide-ethanol mixed solvents. Factors such as solvent viscosities and densities appear to play less dominant roles.

</span></span>