Determination of thermochemical properties of lead vanadates

The standard molar enthalpy of formation(Delta H-f(298.15K)degrees)of five ternary compounds in the Pb-V-O system, namely, PbV2O6 (s), Pb2V2O7 s), -Pb3V2O8 (s), Pb4V2O9 (s) and Pb8V2O13 (s) were determined employing room temperature solution calorimetry and the values obtained are - 1842. 0 +/- 1.0, - 2062.4 +/- 2.3, - 2183.0 +/- 4.0, - 2342.3 +/- 3.2, - 3549.0 +/- 5.0 kJ-mol(-1), respectively. The enthalpy increment of these compounds were measured using a high temperature calvet calorimeter in the temperature range of 325-985 K. From the enthalpy increment data, the temperature dependence of molar heat capacities of these compounds was derived.