Thermodynamics of the formation of cerium(IV) malonate complex and the kinetics of its redox decomposition

Resumo

Thermodynamic and kinetic characteristics of cerium(IV) malonate complex formed in the first stage of cerium(IV) oxidation by malonic acid H₂Mal are studied using a spectrophotometer, a photometer, and a pH-meter at a ionic strength of I = 2 in the pH region of 0.3–1.6 in a sulfuric acid medium at a temperature of 296.8 K. Its composition is found to be CeOHMal⁺. The form of organic ligand is Mal²⁻; the thermodynamic parameters of its formation and kinetic parameters of its intramolecular redox decomposition are determined. The most likely scheme of the initial stages of redox proceeding in the Ce⁴⁺–SO₄^2-–H₂Mal system is discussed, and a quantitative model of it is proposed.