ChemInform Abstract: KINETICS AND MECHANISM OF THE OXIDATION OF URANIUM(III) BY COBALT(III) IN PERCHLORATE MEDIA

The kinetics of the oxidation of U(III) by Co(III) was studied in perchlorate media. The rate law of the reaction was found to be given by the expression -d[Co(III)]/dt = k1 [Co(III)][U(III)]. The value of k1 was determined as (1.12 ± 0.1) x 106 M-1 sec-1 at 20°C and ionic strength of 2.00 and was found to be independent of acid concentration at constant ionic strength. The temperature dependence of the reaction was studied in the range 11 to 31°C, and the values of ΔH2+ and ΔS2+ were determined as 2.00 ± 0.25 kcal mole-1 and -25.6 ± 0.8 cal deg-1 mole-1, respectively. In common with many other reactions of Co(III), the rate constant of this reaction is much lower than expected from the very high ΔG0 value and plausible reasons for this observation are discussed.