Molar Gibbs energy of formation of NaUO3(s)

Abstract

The sodium pressure over the coexisting phase field, NaUO 3 + Na 2 U 2 O 7 + Na 2 UO 4 was measured using Knudsen effusion mass loss (KEML) and Knudsen cell mass spectrometric (KEMS) methods. The sodium pressure over the coexisting phase field can be represented by: log p Na ( Pa ) ± 0.041 = −22701/ T (K) + 17.92 (1117–1193 K). The oxygen potential existing over the above phase field was determined by an oxide electrolyte galvanic cell with air and Ni(s) + NiO(s) as reference systems and can be given by: Δμ ( O 2 ) (kJ/mol) ± 0.19 = −716.9 + 0.335 T (K) (968–1118 K). The molar Gibbs energy of formation of NaUO 3 calculated from the oxygen and sodium potentials can be represented by: ΔG ° f ( NaUO 3 ), T (K) ± 13.4 kJ/mol = −1487.4 + 0.291 T (K). The second and third law treatment of the present data yielded the standard enthalpy of formation, ( Δ f H ° m , 298.15 K) value of (− 1481.4 ± 13.4) and (−1476.8 ± 13.4) kJ/mol respectively.