The enthalpy of ionization of water between 273 and 323 K

Abstract

Calorimetric measurements of the enthalpy of neutralization of hydrochloric acid with excess 0.01 mol kg −1 sodium hydroxide have been made at six temperatures between 273 and 323 K. The enthalpies of dilution of the hydrochloric acid used were determined at the same temperatures. To derive the standard enthalpy changes, ΔH f o, values of enthalpies of dilution were calculated from dilution and heat-capacity data at 298.15 K. The corrections were small and we believe that the uncertainty in these values does not seriously affect the accuracy of the derived ΔH f o values. Heat-capacity changes for the ionization of water have been derived; at 298.15 K the value −(214 ± 5) J K −1 mol −1 is obtained.