Standard enthalpy of formation of aqueous titanyl chloride, TiOCl2(aq), at T = 298.15 K

Enthalpies of solution of TiCl4(l) in aqueous perchloric acid have been measured in an isothermal calorimeter at T = 298.15 K at ionic strengths of (1.964, 3.002, and 4.062) mol · kg−1. These results were extrapolated to zero ionic strength using an extended Debye–Hückel equation, to yield the standard enthalpy of solution ΔslnHm∘(T=298.15K)=-(268.03±0.45)kJ·mol-1; from which the standard partial molar enthalpy of formation of the titanyl ion was derived: ΔfHm∘(TiO2+,aq,T=298.15K)=-(689.4±4.3)kJ·mol-1.