Thermodynamics of lanthanum uranosilicate

Abstract

The standard enthalpy of formation at 298.15 K of crystalline La(HSiUO6)3·10H2O (−10 774.0 ⊥ 13.5 kJ mol−1) and the standard enthalpy of dehydration of this crystal hydrate were determined by reaction calorimetry. The heat capacity of the compound in the range 80–300 K was measured by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. The standard entropy at 298.15 K is −3674.1 ⊥ 1.2 J mol−1 K−1, and the Gibbs energy of formation at 298.15 K, −9678.5 ⊥ 14.0 kJ mol−1. The standard thermodynamic functions of the reactions yielding lanthanum uranosilicate were calculated and analyzed.