Study of the kinetics and activation parameters of reduction of Mn(III) to Mn(II) by SO3 2− ion in (MnSiW11O40H2)5- heteropoly ion

Abstract

In order to gain an insight into the mechanism of reduction of Mn(III) heteropoly ions, and also to establish the conditions for use of some of these ions as oxidizing agent, following measurements have been made. The pseudo-first order rate constants, kobs, have been determined and specific rate constants, k, were calculated from the plots of kobs against SO3 2− concentrations. A plot of ln(k2/T) against inverse temperature gives enthalpy of activation as 10.67 kJ mol−1 and entropy of activation as −237.90 J K−1 mol−1. Effects of ionic strength and pH have also been studied over a limited range.