The kinetics of the reduction of tetraoxoiodate(VII) by n-(2-hydroxylethyl)ethylenediaminetriacetatocobaltate(II) ion in aqueous perchloric acid

The stoichiometries, kinetics and mechanism of the reduction of tetraoxoiodate(VII) ion, IO 4 − to the corresponding trioxoiodate(V) ion, IO 3 − by n -(2-hydroxylethyl)ethylenediaminetriacetatocobaltate(II) ion, [CoHEDTAOH 2 ] − have been studied in aqueous media at 28 °C, I = 0.50 mol dm −3 (NaClO 4 ) and [H + ] = 7.0 × 10 −3 mol dm −3 . The reaction is first order in [Oxidant] and [Reductant], and the rate is inversely dependent on H + concentration in the range 5.00 × 10 −3 ≤ H + ≤ 20.00 × 10 −3 mol dm −3 studied. A plot of acid rate constant versus [H + ] −1 was linear with intercept. The rate law for the reaction is: where a = 8.0 × 10 −4 s −1 and b = 8.40 × 10 −3 dm 3 mol −1 s −1 . Positive salt effect was observed from the rate dependence on ionic strength studies, and added ion showed catalysis of reaction rate. An outer-sphere mechanism is proposed for the reaction.