Spectrophotometric Investigation of Redox Reaction between Methyl Orange and Tetraoxomanganate(VII) Ions in Aqueous Acidic Medium: Kinetics and Mechanistic Approach

Abstract

The spectrophotometric investigation of the redox reaction between methyl orange (here after referred to as MO) and tetraoxomanganate (VII) has been studied in aqueous acid using sodium chloride (NaCl) as an ionic strength I = 0.50 Cmol dm-3, hydrogen ion concentration = 1.0 * 10-3 mol/dm3 (H2SO4) and Temperature = 24±1 0C. The redox reaction showed a stoichiometry of 2:1 and the overall reaction conforms to the rate law: -d[MO]/dt =k2[MO][MnO-4]. The reaction is first order with respect to both the oxidant and reductant concentrations. Lack of polymerization from this reaction suggests probable absence of free radical formation during the course of the reaction. The rate of reaction showed lack of hydrogen ion concentration dependence. The result of ionic strength showed zero effect on the rate of the reaction. Added ions catalyzed the rate of the reaction. Outersphere mechanism is proposed for this reaction.