Absolute enthalpy of hydration of the proton using data for doubly-charged complex ions

Abstract

The method used by Halliwell and Nyburg to estimate the absolute enthalpy of hydration of the proton using data for singly-charged ions has been extended to larger, doubly-charged, complex ions. Certain heats of solution were determined for salts containing complex ions, other data were taken from published values. The result, ΔH°₂₉₈(abs. hyd.) H⁺(g)=– 1095 ± 20 kJ mol^–1, is in close accord with that obtained previously, – 1090.8 ± 10.5 kJ mol^–1. By far the largest source of uncertainty in this value is the lack of reliable lattice energies.