Thermodynamic properties of Co3+(aq)

Abstract

Improved values of the thermodynamic properties of Co³⁺(aq) at 298.15 K have been calculated: Δ_fH_m^⊖(Co³⁺,aq)= 79 ± 7 kJ mol^–1;Δ_fG_m^⊖(Co³⁺,aq)= 131 ± 4 kJ mol^–1;S_m^⊖(Co³⁺,aq)=–341 ± 25 J K^–1 mol^–1. The value of S_m^⊖(Co³⁺,aq) is considerably more negative than that of S_m^⊖(Fe³⁺,aq), a difference which can be related mainly to the small ionic radius associated with the d⁶ low-spin state. Other calculations suggest that the stabilizations with respect to the high-spin state are ΔH_m^⊖= 46 ± 20 kJ mol^–1 and ΔG_m^⊖= 38 ± 25 kJ mol^–1.