Standard enthalpy of formation of La2Te3O9 and La2Te4O11

Abstract Lanthanum tellurites, La 2 Te 3 O 9 and La 2 Te 4 O 11 , 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 La 2 Te 3 O 9 (s), La 2 Te 4 O 11 (s), La 2 O 3 (s) and TeO 2 (s) in 0.150 dm 3 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 La 2 Te 3 O 9 (s) and La 2 Te 4 O 11 (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.