The standard molar enthalpies of formation of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) by solution calorimetry

Abstract The standard molar enthalpies of formation of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) at 298.15 K were determined using an isoperibol calorimeter. The enthalpies of solution of ternary compounds, namely, PbBi12O19(s) and ϕ-Pb5Bi8O17(s) as well as stoichiometric oxide mixtures, namely, {PbO(s) + 6 Bi2O3(s)} and {5 PbO(s) + 4 Bi2O3(s)} in HNO3 (aq., 4.47 mol kg-1) at T = 298.15 K were measured. Using these values, (298.15 K) of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) were determined as (-3549.6 ± 23.8) kJ mol-1 and (-3239.4 ± 7.6) kJ mol-1, respectively. The given uncertainties were calculated as 2σ of the mean with 0.95 level of confidence.