Kinetics and Mechanisms of Oxidation of Thiosuphate Ion by Peroxodisulphate

The kinetics of the oxidation of thiosulphate ion S2O32 by peroxodisulphate ion S2O82- been studied out in system of high ionic strength and phosphate medium at 400C. Under controlled conditions of ionic strength around one (I1) and constant cation concentration the reaction is of overall second order, being first order with respect to each peroxodisulphate and thiosulphate ions. The reaction takes place according to the stoichiometry S2O82- + S2O32- 2SO42- + S4O62- and the rate law R0=k1 [S2O82-]0+ k20 [S2O82-]0 [S2O32-]0+{kMi+ [M+]} [S2O82-]0 [S2O32-]0 Cations catalyze the reaction rate in the ascending order (Li+ less than Na+ less than K+) and the extent of catalysis depends on the nature and concentration of the cations. The activation parameters have been evaluated and discussed and the mechanism has been proposed for the reaction.