Solvation and Free-energies of Transfer of Single ions

Department of Chemistry, University of Kalyani, Kalyani, Nadia, W. Bengal

Department of Applied Chemistry, University of Calcutta, 92, Acharya P. C. Road, Calcutta-700 009, India

Experimental determinations yield changes of thermodynamic parameters associated with neutral combinations of ions (electrolytes) but offer no means of separation of these into components associated with the constituent ions. Yet 'single ion thermodynamics' is a legitimate branch of physical chemistry. The free energies of transfer of ions from one solvent to another, know as 'medium effect. may throw light on ion solvent interactions. Further it will lead to a unified emf series, independent of the solvent, referring the standard electrode potential in different solvents to a single arbitrarily chosen point, i.e., in a reference solvent which can conveniently be the standard hydrogen electrode in the reference solvent.

The status of our knowledge towards understanding 'medium effect' or estimation of free energies of transfer single ions bas been presented through a brief survey of both theoretical and experimental approaches.