The standard molar enthalpy of formation of ThMo2O8

The molar enthalpies of solution of ThMo2O8, Mo, and ThF4 in (10 mol dm−3 HF(aq) + 4.41 mol dm−3 H2O2(aq)) have been measured using an isoperibol calorimeter. From these results and other auxiliary data, the standard molar enthalpy of formation of ThMo2O8 has been calculated to be ΔfHm0(298.15 K) = (−2742.2 ± 4.5) kJ mol−1. This value of enthalpy of formation of ThMo2O8 is consistent with the second law enthalpy of formation of ThMo2O8 determined in this laboratory by transpiration technique.