APPLICATION OF THE MEAN SPHERICAL APPROXIMATION TO DESCRIBE THE ENTROPY OF SOLVATION OF SPHERICAL IONS IN POLAR-SOLVENTS

The entropy of solvation of monoatomic ions in polar solvents is considered within the context of the mean spherical approximation which is used to estimate the experimentally observed quantities in 15 different polar solvents. The role of ion-dipole interactions in determining both the Gibbs energy and entropy of solvation is assessed. It is shown that the temperature variation of the polarization parameter, which characterizes short-range electrostatic interactions, plays an important role in determining the magnitude of the entropy. Not only does this temperature coefficient depend on whether the ion is a cation or an anion, but also on the charge on the ion. The model developed here, together with the parameters extracted from experimental data for monoatomic ions, is applied to estimate the entropic change associated with a simple spherical redox system, namely, ferrocenium cation-ferrocene, which has been used as a model reaction for considering solvent effects on thermodynamic parameters.