Thermodynamic parameters of electrolyte solutions in nitromethane

Abstract

Standard enthalpies of solution of eighteen 1:1 electrolytes in nitromethane derived from heats of solution measured calorimetrically at 298 K are reported. Combination of these data and those in water yields enthalpies of transfer, ΔH°_t, for these electrolytes from water to nitromethane. The Ph₄AsPh₄B convention has been used to derive single-ion ΔH°_t contributions for seven cations and six anions. These data and those previously reported for single-ion free energy of transfer from water to nitromethane enables the calculation of the transfer single-ion entropies based on the Ph₄AsPh₄B convention. As in transfers from water to other non-aqueous solvents ΔS°_t(M⁺+ X^–) from water to nitromethane is approximately independent of M⁺ and X^– when M⁺= Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ and X^–= ClO^–₄, I^–, Br^– and perhaps Cl^–. The results obtained indicate that ΔH°_t for the alkali-metal cations between dipolar aprotic solvents derived from heat of complexing data of cryptand 222, and these cations in these solvents yield single-ion values for transfer among dipolar aprotic solvents that are chemically reasonable and in accord with values obtained by the Ph₄AsPh₄B convention.