Current location: JICS Archive > Vol. 5 > No. 4 > Articles : 14

Kinetics and Mechanism of the Oxidation of a Ferrous Complex with an α,α′-Diimine Chelate Ligand by Ceric Sulfate in Aqueous Acidic Medium by  UV-Vis Absorption Spectroscopy

R. Khattak*, I. Imam Naqvi and M. Akhyar Farrukh

Department of Chemistry, University of Karachi, Karachi - 75270, Pakistan

Kinetics of the oxidation of tris(2,2′-bipyridine)iron(II) sulfate by ceric sulfate was spectrophotometrically studied in an aqueous sulfuric acid medium. Different methods, including isolation, integration and half-life, were employed to determine the reaction order. The redox reaction was found to be first-order with respect to the reductant, tris(2,2′-bipyridine)iron(II) sulfate, and the oxidant, ceric sulfate. Complex kinetics was observed with an increase in the initial concentration of the oxidant. The influence of the dielectric constant, [H⁺] and [SO₄^2-] on the rate was also investigated. The increase in the dielectric constant and H⁺ ion concentration of the medium retard the rate, while an increase in the SO₄^2- ion concentration first accelerates the rate, and then retards the reaction. The effect of each factor, i.e., the dielectric constant, H⁺ ions and SO₄^2- ions, suggests that Ce(SO₄)₃^2- is the active species of cerium(IV).

Keywords: Kinetics and mechanism, UV-Vis absorption spectroscopy, Redox reaction, Tris(2,2′-bipyridine)iron(II) sulfate, Ceric sulfate