The thermodynamics of solvation of ions. Part 2.—The enthalpy of hydration at 298.15 K

So-called ‘absolute’ standard molar enthalpies of hydration of individual ions at 298.15 K have been obtained from the conventional data by means of the widely employed TATB extrathermodynamic assumption, i.e. that ΔhydH°[(C6H5)4As+]=ΔhydH°[(C6H5)4P+]=ΔhydH°[B(C6H5)–4]. This is possible by the evaluation of the standard molar enthalpies of hydration of salts involving the tetraphenyl ions with suitable counter-ions from their lattice enthalpies and heats of solution and appropriate combinations of these data. The resulting value of the standard molar enthalpy of hydration of the hydrogen ion, ΔhydH°[H+]=–1103 ± 7 kJ mol–1, agrees with the values obtained by other reliable methods. The values of ΔhydH° on this basis of numerous ions are tabulated.