Publisher: Chemical Society of Nigeria

Studies Into The Kinetics and Mechanism of The Redox Reaction of Malachite Green and Nitrite Ions In Aqueous Acidic Medium.

Y. Mohammed, J. F Iyun, O. Idris
KEYWORDS: redox, kinetics, mechanism, catalysis, salt effect


Studies into the redox kinetics and mechanism of the reactions of malachite green (MG+) and NO2– were carried out in aqueous acidic medium, at a temper–3 (Na2SO4), [H+] = 5.0 x 10–3 mol dm–3 (H2SO4). One mole of the dye was found to be consumed by one mole of NO2–, as stoichiometric studies showed. The reaction is first order in both [MG+] and [NO2–].The rates of redox reaction showed dependence on acid concentrations (in the acid range used). Rate equation for the reaction has been proposed as: –d[MG+]/ dt =(a[H+])[MG+][NO2–]. The second order rate constant for the malachite green – NO2– reaction was found to be (6.24 ± 0.02 ) x 10–3 dm3 mol–1 s–1 . The rates of reaction displayed positive salt effect. Log k1 versus 1/D gave negative slope for the reaction. Added anions and cations had no effect on the reaction. Results of the Michaelis- Menten analysis gave an evidence of intermediate complex formation. Based on the results obtained experimentally, the inner – sphere mechanism is proposed for the malachite green – NO2– reaction.

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