Oxygen Potential in the System UMoO6/UMoO5 by the Solid Oxide Electrolyte Emf Method

The emf of the galvanic cell Pt|UMoO₆UMoO₅|ZrO₂-Y₂O₃|O₂(air, Po₂=0.21 atm)|Pt, measured from 776 to 1127 K, was determined to be E = 751.7?0.4909 ±4.3 mV. Using the standard Gibbs energy of formation, ^fΔG°, for UMoO₆ reported in the literature from transpiration studies, the ^fΔG° for UMoO₅ is calculated to be ^fΔG°〈UMoO₅〉=?1816.9+0.3748T±6.0 U-mol^?1 The magnitudes of the standard entropies of formation, ^fΔS°, for UMoO₆ and UMoO₅ were evaluated from those values reported for the binary oxides which constitute the ternary compounds.