Thermodynamic studies on Ba2.875UO5.875(s)

The Gibbs energy of formation of Ba2.875UO5.875(s) has been determined using manometric technique. The equilibrium CO2(g) pressures over the three phase mixture: {Ba2.875UO5.875(s) + Ba3UO6(s) + BaCO3(s)} have been measured using an absolute pressure transducer in the temperature range 1030–1220 K. The corresponding Gibbs energy expression as a function of temperature can be given as:ΔfGm°(T)(Ba2.875UO5.875,s,T)   (kJ   mol−1)±5=−3153.1+0.5573   (T/K)ΔfHm°(298.15 K) and Sm°(298.15 K) data have been calculated from the above Gibbs energy expression using required values from the literature. The corresponding values are −3143.4 ± 2 kJ mol−1 and 270.8 ± 4 J K−1 mol−1, respectively. The ΔfHm°(298.15 K) value has also been calculated from third law method as −3137.7 ± 4 kJ mol−1.