Use of SnO for the determination of standard Gibbs energy of formation of SnO2 by oxide electrolyte e.m.f. measurements

Evidence was obtained from DTA for the disproportionation of SnO into Sn(1) and SnO2 at 815 K below a heating rate of 20 degreesC/min in helium and at 800 K in air at 10 degreesC/min heating rate. The e.m.f. of a galvanic cel l with SnO/SnO2 and Sn(1)/SnO2 as electrodes using 15 mol% YO1.5 stabilised ZrO2 (15 YSZ) as the electrolyte showed SnO disproportionation into Sn and SnO2 to be complete by about 750 K, The e.m.f. of the galvanic cells with SnO/SnO2 as the test electrode, N-2 (P-O2 approximate to 10(-3) atm)/Pt or Fe/FexO as the reference electrodes and with 15 YSZ as the electrolyte meas ured over the ranges 776-1140 and 772-1206 K, respectively, yielded the exp ression DeltaG(f)(0)(SnO2) +/- 2.2 (KJ mol(-1)) = -568.9 + 0.2007T (K) for the standard Gibbs energy of formation of SnO2, A third-law analysis of the e.m.f. data yielded -578.3 +/- 4.0 kJ mol(-1) for the standard enthalpy of formation, DeltaH(1.298)(0) of SnO2(s). (C) 2001 Elsevier Science B.V. All rights reserved.