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

Abstract The Gibbs energy of formation of Ba 2.875 UO 5.875 (s) has been determined using manometric technique. The equilibrium CO 2 (g) pressures over the three phase mixture: {Ba 2.875 UO 5.875 (s) + Ba 3 UO 6 (s) + BaCO 3 (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: Δ f G m ° ( T ) ( B a 2 .875 U O 5 .875 , s, T ) ( kJ   mol − 1 ) ± 5 = − 3153.1 + 0.5573 ( T / K ) Δ f H m ° (298.15 K) and S m ° (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 Δ f H m ° (298.15 K) value has also been calculated from third law method as −3137.7 ± 4 kJ mol −1 .