Ion-solvent Interaction

 Solution is a  homogeneous phases made up of  solute and solvent in different ratios. In solution, the solute is dispersed uniformly throughout the solvent. Normally, the component which is in excess is called the solvent and the minor component is the solute.  Solvent may be a pure liquid or it may be a mixture of two or more liquids. For example sodium chloride solute is dissolved in water (solvent)  forms NaCl solution in aqueous medium. The solution is neutral in nature as it contains equal number of hydrogen and hydroxyl ions.

Solvents containing Hydrogen ion donor groups are called protic solvents. The dielectric constant of these solvents are generally high. Solvent which acts as proton donor and proton acceptors are called amphiprotic solvents . Water, alcohols,amides etc are the best examples for this type of solvent.

Ion-Solvation

Ion-solvation is the important term that describes all type of ion-solvent interactions. The electrolytic solution contains an electrolyte in ionized form either completely or partially. The ionisation of an electrolyte in solution indicates the ion-solvation. The solubility of electrolytes are greatly affetced by the solvation of their constituent ions.

The term solvation refers to the surrounding of each dissolved molecule or ion by a shell of more or less tightly bound solvent molecules. This solvent shell is the result of intermolecular forces between solute and solvent. For aqueous solutions the term used is hydration. During the dissolution process, when a relatively small amount of solute dissolves in relatively large amount of solvent to form a homogeneous phase, a variety of intermolecular forces play a role such as solvent-solvent interaction, solute-solvent interaction and solute-solute interaction.

The study of ion-solvation in water and mixed solvents(water + organic) has proliferated in recent years because of its importance due to the availability of techniques and also its foreseeable applications. The technique that have been evolved mainly electrochemical and spectroscopic applications are for instance, in the field of high energy density batteries, hydrometallurgy, determination of simple ion Gibbs energy changes, in the preparation of model for polar clusters, in preparation of ion-selective PVC membrane electrodes in determination of structure of ion-solvation state of bimetallic salts and its derivatives  in solvents, determination of bulk single ion solvation enthalpies , ion association of complexes in pure and mixed solvents etc