The standard molar enthalpies of formation of Pb2CrO5(s) and Pb5CrO8(s) by acid solution calorimetry

The standard molar enthalpies of formation, ΔfHm∘ (298.15 K) of Pb2CrO5(s) and Pb5CrO8(s) were determined using an isoperibol calorimeter. The enthalpies of solution of pure compounds, viz., Pb2CrO5(s), and Pb5CrO8(s) as well as mixtures viz., {PbCrO4(s) + PbO(s)} and {PbCrO4(s) + 4PbO(s)} in HNO3 (aq., 8 mol · dm−3) at T = 298.15 K were measured. Using these values, ΔfHm∘ (298.15 K) of Pb2CrO5(s) and Pb5CrO8(s) were determined as −(1171.5 ± 1.7) kJ · mol−1 and −(1850.6 ± 8.7) kJ · mol−1, respectively.

Research highlights
► Acid solution calorimetry studies to determine the enthalpy of formation of ternary compounds in (Pb + Cr + O) system.
► Standard molar enthalpy of formation of lead chromates at 298 K.
► The standard enthalpy of formation of Pb2CrO5(s) is –1171.5 ± 1.7 kJ · mol−1.
► The standard enthalpy of formation of Pb5CrO8(s) is −1850.6 ± 8.7 kJ · mol−1.