Abstract :
The standard molar reaction enthalpies of two reactions, LaCl3·7H2O(s)+3CCl3COOH(s) (or TCA)=La(TCA)3·3H2O(s)+3HCl(g)+4H2O(l) and La(TCA)3·3H2O(s)+2C9H7NO(s)=La(TCA)(C9H6NO)2(s)+2CCl3COOH(s)+3H2O(l), were studied by classical solution calorimetry. The molar dissolution enthalpies of the reactants and the products of the two reactions in certain solvent (for one reaction is in 1 mol/l HCl and another in a mixed solution consisting of absolute ethyl alcohol, dimethyl sulfoxide and 4 mol/l HCl) were determined by using an isoperibol calorimeter. From the results and other auxiliary quantities, the standard molar formation enthalpies of [La(TCA)3·3H2O, s, 298.15 K] and [La(TCA)(C9H6NO)2, s, 298.15 K] were determined to be ΔfHmΘ[La(TCA)3·3H2O, s, 298.15 K]=−3063.3 kJ/mol and ΔfHmΘ[La(TCA)(C9H6NO)2, s, 298.15 K]=−1375.6 kJ/mol.
