Solvation of HCI in Water-Acetone Mixtures

Abstract

Activity coefficients of HCl in water-acetone mixture and thermodynamic quantities for the transfer of HCl from water to the mixed solvents at 25°C were determined by EMF measurements of the cell: H1⁺ glass electrode HCl in mixed solvent AgCl-Ag. These thermodynamic quantities were tentatively divided into the contribution of solvation layer consisting of solvent molecules reoriented to ions and that of the bulk region arising from the difference in dielectric constants, and the quantities of the latter were estimated from the electrostatic model by taking the value of 0.41 nm for the radius of solvated ion. The contribution of solvation layer to entropies and enthalpies of the transfer of HC1 from water to water-acetone mixture decreases with an increase in the concentration of acetone, but the contribution of solvation layer to free energies of transfer gradually increases, because of the quantities of the former being always larger than those of the latter. The thermodynamic quantities were discussed in terms of ion-solvent interactions as well as the structual changes of the solvents.