The enthalpies of solution and neutralization of HF(I); enthalpies of dilution and derived thermodynamic properties of HF(aq)

Abstract

Enthalpies of solution, ΔHsoln, of HF(I) in water and the enthalpy of neutralization, ΔHN, of HF(I) in dilute NaOH, as well as some enthalpies of dilution, ΔHdlln, of HF(aq) were measured in a reaction calorimeter. These results were combined with some enthalpies of dilution of HF(aq) reported in the literature to obtain the enthalpy of solution of liquid HF as a function of composition between HF·∞H2O and HF·H2O. The enthalpies of formation of all aqueous HF solutions in this concentration range were obtained by combination of the enthalpy of formation of HF(I) and the enthalpies of solution of HF(I). In addition, the relative apparent molar enthalpies, Lo, of HF(aq) and the relative partial molar enthalpies, L2 and L1, of HF and H2O, respectively, were calculated. Some of the key measured and derived results at 298.15 K obtained in this work are ΔHoN(HF, 1) = - (21017 ± 29) calth mol−1, ΔHosoln(HF, 1) = − (7672 ± 38) calth mol−1, and ΔHot,(HF, aq) = ΔHof(F−, aq) = − (80.22 ± 0.07) kcalth mol−1.