Standard enthalpy of formation of La2Te3O9 and La2Te4O11

Lanthanum tellurites, La2Te3O9 and La2Te4O11, have been prepared by the solid state synthesis route and characterized for their phase and chemical compositions by XRD and ICP-AES analyses. The molar enthalpies of solution of La2Te3O9(s), La2Te4O11(s), La2O3(s) and TeO2(s) in 0.150 dm3 of 10.98 mol dm−3 HCl were measured using an isoperibol calorimeter. From these results and other auxiliary data the standard molar enthalpy of formation of La2Te3O9(s) and La2Te4O11(s) were derived to be (−2814.6 ± 12.9) kJ mol−1 and (−3116.5 ± 17.3) kJ mol−1, respectively, at 298.15 K which are the first reported thermodynamic data on these compounds at 298.15 K.