Kinetics and mechanism of iridium(III) catalysed oxidation of tellurium(IV) by cerium(IV) in sulfuric acid medium

Department of Inorganic and Analytical Chemistry, Andhra University, Visakhapatnam-530 003, India Manuscript received 13 July 2000. revised 27 November 2000, accepted 10 February 2001 The kinetics and mechanism of iridium(iii) catalysed oxidation of tellurium(iv) by cerium(iv) have been studied in sulfuric acid medium. The reaction is first order in [IrIII] as well as in [CeIV] and fractional order (0.23) in [TeIV]. Increase in [H3O+] accelerates the rate while that in ionic strength or \(H_2SO_4^-\), retards. CeIII, one of the products, inhibits while the other, TeIV, has negligible effect on the rate. The reaction is supposed to proceed via the formation of a complex between TeIV and IrIII which in turn reacts with active Ceiv species in a reversible step. A rate law, consistent with the observed kinetic data, has been derived basing on the proposed mechanism