Thermodynamic stability of Sb2O4 by a solid oxide electrolyte e.m.f. method

The standard Gibbs energy change for the reaction Sb₂O₃ (orthorhombic) (orthorhombic) was measured using the following galvanic cell: Pt, Sb₂O₃(ortho), Sb₂O₄ (ortho), platinum black |15 Wt % Y₂O₃-stabilized ZrO₂|O₂(air,P _{o 2} = 0.21 atm), Pt over the range 585 to 828K. Reproducible e.m.f. values were obtained only when the otherwise poorly electronic conducting oxide mixture was blended with platinum black. The standard Gibbs energy change forthis reaction was found to be (G_R ^o ± 0.81) (kJ) = –16833 + 0.0S019T/K. This yielded thestandard Gibbsenergy offormation G_R ^o of Sb₂O₄ (ortho) to be as follows: \gDG₁ ^o(Sb₂O₄, ortho) \+- 1.61] (kJ) \s= \t-854.89 \s+ 0.33614T/K. A third-law treatment yielded a value of \t-880.55 (\+-1.21) kJmol^\t-1 for \gDH _1,298 ^o of Sb₂O₄ (ortho).