OXIDATION OF ETHYLENEDIAMINETETRAACETATOCOBALTATE(II) COMPLEX BY HYDROGEN PEROXIDE IN AQUEOUS ACIDIC MEDIUM: A KINETIC STUDY

A.D. Onu, S.O. Idris, J. FIyun

Abstract


The oxidation of ethylenediaminetetraacetatocobaltate(II) complex ([CoEDTA]2-) by Hydrogen peroxide  in aqueous perchloric acidic medium was   studied at ionic strength (I) 0.50 mol dm-3 (NaClO4), T = 30 0C , [H+] = 110-3 mol dm-3  and  λmax of  510  nm. Stoichiometric determination shows that for two moles of   the reductant, one mole of the oxidant was consumed. Kinetics study carried out under pseudo - first order condition gave result that fit into the rate law: The study on the effect of [H+] on the rate of reaction shows that the rate and acid concentration varies inversely and the plot of  acid dependent rate constant against [H+]-1 was linear with  slope 2.0  10-7 dm3 mol-1 s-1 and intercept 1.0 10-4 s-1 . The rate law involving acid concentration is:The   reaction displayed negative primary salt effect which suggests the composition of activated complex are oppositely charged reactants ions.  The Michaelis – Menten’s plot gave significant intercept indicative of presence of intermediate complex. On the basis of available evidence the inner - sphere mechanism is proposed for the reaction.

Keywords: Oxidation, Ethylenediaminetetraacetatocobaltate(II), Complex, Hydrogen Peroxide, Kinetics 


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Chemical Society of Nigeria