Browsing by Author "Tanimu, A."

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    Kinetics and Mechanism of Malachite Green Oxidation by Hypochlorite Ion in Aqueous Acidic Medium
    (Deapartment of Chemistry, Nasarawa State University Keffi, 2014-11-11) Idris, S.O.; Tanimu, A.; Iyun, J.F.; Mohammed, Y.
    The kinetic investigations of the redox reaction between malachite green, MG+, and hypochlorite ion, ClO–, were carried out in aqueous HClO4 medium at [H+] = 1x10–3 mol dm–3, µ = 0.1 mol dm–3, T = 25±1°C. The reaction showed a stoichiometry of 1:2, which conforms to the equation: MG+ + 2ClO– Products Kinetic data revealed a first order dependence on both [MG+] and [ClO-] giving a second order overall. The second order rate law for the reaction conforms to the equation: −d[MG+]/dt = k2[MG+][ClO-] where k2 = 115.55± 1.21 dm3 mol-1 s–1 Reaction rate increased with increase in [H+]. Changes in ionic strength and dielectric constant of the reaction medium did not alter the reaction rate. Addition of anions at different concentrations also did not affect reaction rate. The absence of spectroscopic evidence of intermediate complex formation suggests that the reaction proceeds through the outersphere mechanism. This suggestion is further reinforced by kinetic evidence from the Michaelis-Menten plot. A plausible mechanism based on these observations is proposed.
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    Kinetics and Mechanism of the Reaction of Malachite Green and Dithionite Ion
    (Deparment of Chemistry, Nasarawa State University Keffi, 2014-11-11) Idris, S.O.; Tanimu, A.; Iyun, J.F.; Mohammed, Y.
    The kinetics of the oxidation of malachite green, MG+, by dithionite ions, S2O42- have been studied spectrophotometrically in an aqueous acid free medium. The investigation was carried out under pseudo- first order conditions of an excess of dithionite concentration. Reaction conditions were ionic strength of reaction medium, µ = 0.1 mol dm–3, λmax = 620nm and T = 25.5±0.5°C. The stoichiometry of the reaction, determined by spectrophotometric titration, was 1:1. Reaction rates increased with increase in µ and dielectric constant (D) of reaction medium. Added ions catalysis of the reaction and the result of the Michaelis - Menten analysis suggest that the reaction proceeded through the outersphere pathway. A plausible mechanism is proposed.