Ion–ion–solvent interactions in aqueous ionic cosolvent systems. I. Transfer thermodynamics of hydrogen chloride in aqueous sodium nitrate solutions from emf measurements

Abstract

Standard potentials (EO) of the Ag-AgCl electrode have been determined in 1. 2, and 4 rn NaN03 + water mixtures at five equidistant temperatures ranging from 15-35°C from the emf measurements of the cell: Pt, H2 (g, 1 atm)/HCl ( m ) NaN03 + water/AgCl-Ag. These values have been used to evaluate the trarisfer energetics (AG?, TAG, and A@) accompanying the transfer of 1 mole of HCl from the standard state in water to the standard state in each of the NaN03 + water mixtures. Transfer free energies AG: of HCl and that of the individual ions obtained from a separate study, and those obtained after correcting the "cavity effect" and Born-type electrostatic effect, as estimated tentatively by the scaled-particle theory (SPT) and simple Born equation respectively, have been discussed in the light of ion-ion-solvent interactions. The observed TAG-composition profile as well as that obtained after correcting for the "cavity effect" were examined in the light of semiquantitative theory proposed by Kundu et al. earlier and are found to substantiate this theory.