Kinetics studies into the redox reaction and mechanism for the reactions of crystal violet (CV+) and MnO4â€“ were carried out in aqueous acidic medium, at [CV+] = 1.6 X 10-5 mol dm-3, [MnO4-] = 8.0 x 10-4 mol dm-3 , [H+] = 2.0 x 10-3 mol dm-3, Âµ = 1.88 x 10-1 mol dm-3 (NaCl), T = 25.0 Â± 1ÂºC and Î»max = 580 nm. The stoichiometric studies showed that one mole of the crystal violet was found to be consumed by two mole permanganate ion. The reaction is first order with respect to [MnO4â€“]. The [H+] varied in the range (0.4 â€“ 4.0) x 10-3 mol dm-3 showed dependence on acid concentrations (HCl). Rate equation for the reaction has been proposed as:
â€“d[CV+]/ dt = (a + b[H+])[CV+][MnO4â€“].
Where a = 0.5 x 10-4 dm3 mol-1
b = 5.0 x 10-1 dm3 mol-1
The second order rate constant for the crystal violet â€“ MnO4â€“ reaction was found to be (1.90 Â± 0.05) dm3 molâ€“1 sâ€“1. The reaction showed zero salt effect. Result for dielectric constant (D) shows negative effect while added anions shows positive effect. Spectroscopic test indicate a shift in Î»max while Michaelis-Menten analysis indicate the absence of intermediate complex formation. Based on the experimental results obtained, the outer â€“ sphere mechanism is proposed for the reaction of CV+ / MnO4â€“.
Keywords: Kinetics, crystal violet, spectroscopy.