MOLAR GIBBS ENERGY OF FORMATION OF BAMO2O7(S) USING THE SOLID OXIDE GALVANIC CELL METHOD

Delta(f)G degrees(BaMo2O7, s, T) has been determined using the emf tec hnique. The cell used was: (-)Pt/(BaMo2O7(s)+BaMoO4(s) +MoO2(s))//CSZ/ /air (p(O-2(g) = 21.21 kPa)/Pt(+). The observed emfs in the temperatur e range 828-985 K could be represented by E = 0.7663 - 4.953 x 10(-4)T (+/-0.001) V. The standard molar Gibbs energy of formation of BaMo2O7 (s) was evaluated from emf values and the Delta(f)G degrees(T) of BaMo O4(s) and MoO2(s). The corresponding expression is given as Delta(f)G degrees(BaMo2O7, s, T) = -2269.7 + 0.6173T (+/-5.1.) kJ mol(-1). Using the required literature values, the Delta(f)H degrees(BaMo2O7, s, 298 .15 K) was calculated by the second-law method and the corresponding v alue is -2291.2 kJ mol(-1). The present study is the first experimenta l work for the determination of Delta(f)G degrees(BaMo2O7, s, T). (C) 1997 Academic Press.