Kinetics and mechanism of oxidation of Pyrocatechol Violet by chlorite ion in aqueous hydrochloric acid 

By Adetoro A., Iyun J. F. and Idris S.O. 

ABSTRACT

At I = 0.50 mol dm-3 (NaCl), T = 21 ± 1oC, [H+] = (0.6-1.8) x 10-2 mol dm-3, the oxidation-reduction reaction between pyrocatechol violet (hereafter referred to PCVH) and chlorite ions have been studied and has a stoichiometry of 1:1. The reaction is second-order overall, first-order in both oxidant and reductant. The reaction occurs by parallel acid independent  and acid-dependent pathways suggesting HClO- and ClO2- as the principal reactant chlorite species. The second order rate constant increases with increase in acid concentration and decrease with an increase in ionic strength of the reaction medium. The reaction rate was mildly reduced by anions SO42-   and HCOO-. The test for free radicals was negative. The kinetic data are consistent with the following equation:  


The experimental results are in favour of the outer-sphere mechanisms 

Key Words: Pyrocatechol violet, Chlorite ions, Kinetic, Mechanism.

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