Solvation of Fluoride Ions. II. Enthalpies and Entropies of Transfer From Water to Aqueous Methanol

Abstract

Enthalpies of transfer of potassium fluoride from water to water-methanol mixtures over the whole composition range have been determined by calorimetry. Combination of these values with literature data has enabled calculation of the enthalpies and entropies of transfer for the individual ions through the tetraphenylarsonium tetrapbenylborate ( tatb ) assumption. The values of Δ_tH°(F^-) and Δ_tS°(F^-) show a complex dependence on solvent composition which closely parallels the dependence of the other halide ions. These effects are discussed in terms of ion-solvent and solvent-solvent interactions. The halide ions appear to be (weakly) preferentially solvated by H₂O, and the alkali metal ions by MeOH.