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

Abstract

The standard Gibbs energy change for the reaction Sb₂O₃ (orthorhombic)$+ \tfrac{1}{2}O_2 (g) \rightleftharpoons Sb_2 O_4$ (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 (ΔG_R ^o ± 0.81) (kJ) = −16833 + 0.0S019T/K. This yielded thestandard Gibbsenergy offormation ΔG_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).