Synthesis, characterization and standard molar enthalpy of formation of La(C 7H 5O 3) 2·(C 9H 6NO)

Abstract

The product from reaction of lanthanum chloride seven-hydrate with salicylic acid and 8-hydroxyquinoline, La(C 7H 5O 3) 2·(C 9H 6NO), was characterized by IR, elemental analysis, molar conductance, and thermogravimetric analysis. The standard molar enthalpies of solution of [LaCl 3·7H 2O (s)], [2C 7H 6O 3 (s)], [C 9H 7NO (s)] and [La(C 7H 5O 3) 2·(C 9H 6NO) (s)] in a mixed solvent of absolute ethyl alcohol, dimethyl formamide (DMF) and perchloric acid were determined by calorimetry to be Δ s H m Θ [LaCl 3·7H 2O (s), 298.15 K] = −96.45 ± 0.18 kJ mol −1, Δ s H m Θ [2C 7H 6O 3 (s), 298.15 K] = 14.99 ± 0.17 kJ mol −1, Δ s H m Θ [C 9H 7NO (s), 298.15 K] = −3.86 ± 0.06 kJ mol −1 and Δ s H m Θ [La(C 7H 5O 3) 2·(C 9H 6NO) (s), 298.15 K] = −117.78 ± 0.11 kJ mol −1. The enthalpy change of the reaction (1) LaCl 3·7H 2O (s) + 2C 7H 6O 3 (s) + C 9H 7NO (s) = La (C 7H 5O 3) 2·(C 9H 6NO) (s) + 3HCl (g) + 7H 2O (l) was determined to be Δ r H m Θ = 91.57 ± 0.34 kJ mol −1. From data in the literature, through Hess’ law, the standard molar enthalpy of formation of La(C 7H 5O 3) 2·(C 9H 7NO) (s) was estimated to be Δ f H m Θ [La(C 7H 5O 3) 2·(C 9H 6NO) (s), 298.15 K] = − 2076.5 ± 3.9 kJ mol −1.