Solvent structure effects on electrical conductivities of small-ion salts compared to large-ion salts in C1–C4 alcohols and water

Abstract

The electrical conductances of the small-ion salts LiI and LiNO3 in water and C1–C4 alcohols were measured at different temperatures. At the concentrations used, ion association was negligible except when εT < 4200 K, where ε is the relative permittivity of the solvent at temperature T. Consistent with Walden's rule, the values of ηΛ0 in each solvent are nearly constant as the temperature is increased; the value for LiI in each solvent is slightly higher than that for LiNO3. Ion association occurs in tert-butanol and is more extensive for LiNO3 than that for LiI; the planar NO3− ions fit less well than the spherical I− ions into the packing of the rigid, spherical tert-butanol molecules. The effective radius of solvated ions in CN primary alcohols increases approximately as the length of the randomly folded chain, (N + 1)1/2. For secondary alcohols this factor is somewhat too small for small-ions and too large for large tetraphenyl ions. The values of EΛ0 are close to the values of Eη in the corresponding alcohols. Keywords: electrical conductivity, large ions, small-ions, alcohols, solvent effects.