GIBBS ENERGIES OF FORMATION OF MOO2 AND MO4O11

The Gibbs energies of formation of MoO2 and Mo4O11 have been determined by means of e.m.f. measurements using the cells Mo, MoO2/ZrO2· CaO or ThO2· Y2O3/Fe0.95O, Fe and Fe, Fe0.95O/ZrO2· CaO/Mo4O11, MoO2. The data may be represented by the equations f ΔG0 〈MoO2〉 = -571.8 + 0.1662T ± 1.1 (kJ mol-1) between 1070 and 1320 K and fΔGo〈Mo4O11〉 = -2743 + 0.853T ± 5 (kJ mol-1) between 840 and 1090 K. The enthalpies of formation and standard entropies of MoO2 and Mo4O11 at 298 K are calculated by second law evaluations. fΔH0298 〈MoO2〉 = -(586 ± 3) kJ mol-1S0298 〈MoO2〉 = (49 ± 2) JK-1 mol-1fΔH0298〈Mo4O11〉 = -(2807 ± 12) kJ mol-1S0298〈Mo4O11〉 = (290 ± 15) J K-1 mol-1 The Gibbs energies of formation of MoO2 and Mo4O11 are given by fΔG0〈MoO2〉 = -592 - 0.0387Tlog T + 0.303T (kJ mol-1) between 298 and 2000 K and fΔG0〈Mo4O11〉 = -2776 + 0.886T (kJ mol-1) between 298 and 1091 K. © 1979.