Synthesis of Crystalline Americium Hydroxide, Am(OH)3 and Determination of its Enthalpy of Formation; Estimation of the Solubility-Product Constants of Actinide(III) Hydroxides

摘要: This paper reports a new synthesis of pure, microcrystalline Am(OH){sub 3}, its characterization by x-ray powder diffraction and infrared spectroscopy, the calorimetric determination enthalpy solution in dilute hydrochloric acid. From formation 3} has been calculated to be {minus}1371.2{plus_minus}7.9 kj{center_dot}mol{sup {minus}1}, which represents first experimental an any actinide hydroxide. The free energy solubility product constant (K{sub sp} = 7 {times} 10{sup {minus}31}) have from our entropy estimates are compared with literature measurements under near-equilibrium conditions. Since many properties tripositive lanthanide ions (e.g., hydrolysis, complex-ion formation, thermochemistry) change regular manner, these can interpreted systematically terms ionic size. compares thermochemistry thermochemical studies hydroxides. A combined structural acid-base model is used explain systematic differences enthalpies between oxides hydroxides 4f{sup n} 5f{sup subgroups predict solubility-product constants for actinide(III) Pu through Cf.