Determination of thermochemical properties of lead vanadates

The standard molar enthalpy of formation ΔfH298.15K∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\Delta_{\text{f}} H_{{298.15{\text{K}}}}^{^\circ } } \right)$$\end{document} 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.