Determination of Partial Reaction Orders of the Reduction of Potassium Permanganate by Ethanol in Various Environments

Abstract

A spectrophotometric kinetic study of the reaction of the potassium permanganate reduction by excess ethanol in acidic, neutral and alkaline environments was performed. The reaction mixtures were prepared from the solutions of potassium permanganate of different concentrations (0.0004, 0.001 and 0.002 М) and either the solutions of sulphuric acid (1, 3 and 10 %), water, or the solutions of sodium hydroxide (0.01, 0.04 and 0.1 М). The kinetic curves were recorded with the spectrophotometer at the wavelengths of 525 nm (in acidic environment), 400 nm (in neutral environment) and 605 nm (in alkaline environment). The initial reaction rates were determined from the slopes of the initial linear parts of the kinetic curves. Using the differential van’t Hoff method, the partial reaction orders were determined. It was shown that in the acidic environment the partial reaction order with respect to permanganate is close to 1.5, and that with respect to hydrogen ions is close to 0.6. In the neutral and alkaline environments the reaction obeys the first partial order with respect to permanganate, and the partial order of the reaction in alkaline environments with respect to hydroxyl-ions is close to 0.8. It was also shown that the effective rate constants of the reaction in acidic and alkaline environments are significantly higher than that in neutral environment