THE KINETICS OF THE OXIDATION-REDUCTION REACTION BETWEEN URANIUM(VI) AND TITANIUM(III) IN HCL SOLUTION

The oxidation-reduction reaction between U(VI) and Ti(III) in HCl solu tion was studied spectrophotometrically. The reaction is second-order at all concentrations of reactants, HCl, ferrous chloride and mannitol used in this work. In 5M HCl the rate constant k increases with incre asing Ti(III) concentration, whereas it decreases with increasing U(VI )) concentration, with increasing HCl concentration from 1.00M to 7.17 M and increases thereafter from 7.17M to 11.79M. The addition of manni tol causes a consistent decrease in the rate of reaction, whereas ferr ous chloride has no effect. The activation energy for this oxidation-r eduction reaction was 47.90 +/- 0.11 kJ.mol(-1). The values of Delta H -not equal, Delta G(not equal) and Delta S-not equal were 45.40 +/- 0. 11 kJ.mol(-1), 72.50 +/- 0.17 kJ.mol(-1) and -91.10 +/- 0.22 J.k(-1).m ol(-1), respectively. The mode of reaction is discussed in the light o f kinetic results.