Thermodynamic transfer properties for Na+, Tl+ and Ag+ to water–acetonitrile mixtures

Abstract

Gibbs energies of transfer for Na⁺, for Tl⁺ and for Ag⁺ from acetonitrile to its mixtures with water have been obtained from electrochemical measurements employing the bis(biphenyl)chromium assumption. Entropies of transfer were calculated from the temperature coefficients of electrode potentials and from half-wave potentials on the basis of the assumption of a negligible thermal diffusion potential. Enthalpies of transfer were derived from Gibbs energies and entropies of transfer. Preferential solvation between the soft acceptor, Ag⁺, and the soft donor, acetonitrile, was observed, whereas the hard Na⁺, and also Tl⁺ interacted more strongly with water. The changes for the Gibbs energies of transfer in the solvent mixtures could be accounted for as donor–acceptor (coordinative) interactions between cations and solvent molecules taking into account the principle of hard and soft acids and bases. Changes in the entropies of transfer are discussed on the basis of interactions between entities consisting of the cations with their first solvation shells and the surrounding solvent matrices.