Determination of standard molar Gibbs energy of formation of SrMoO 4(s)

Abstract

An electromotive oxygen concentration cell using calcia-stabilized zirconia (CSZ) electrolyte has been constructed and used to determine Δ f G m o(SrMoO 4, s, T). The e.m.f. of cell (II), Pt/SrMoO 3(s) + SrMoO 4(s)/CSZ/air/Pt, could be represented by E (V) ± 0.006 = 1.515-4.299 × 10 −4 T (K), while the e.m.f. of cell (III), Pt/SrMoO 3(s) + SrMoO 4(s)/ CSZ/Fe x O(s) + Fe(s)/Pt, could be represented by E (V) ± 0.002 = 0.1459 - 5.859 × 10 −5 T (K). The e.m.f. values were combined with Δ f G m o( T) of SrMoO 3(s) and Fe x O(s) from our earlier studies to get Δ f G m o(SrMoO 4, s, T) values as Δ f G m o(SrMoO 4, s, T) (kJmol −1) ± 1.2 = −1582.6 + 0.3692 T (K) (1046.0 ⩽ T ⩽ 1255.5 K) for cell (II) and Δ f G m o(SrMoO 4, s, T) (kJmol −1)± 0.4 = −1583.0 + 0.3699 T (K) (1037.5 ⩽ T ⩽ 1278.0 K) for cell (III). From the variation in Δ f G m o(SrMoO 4, s, T) (kJmol −1) with temperature and the relevant heat capacity values from the literature, Δ f H m o(298.15 K) of SrMoO 4(s) has been obtained as −(1582.9±0.5) and −(1583.3±0.1) kJmol −1 respectively and the average value is −(1583.1±0.6) kJmol −1.