Kinetics of oxidation of arsenic(III) by platinum(IV) in alkaline medium

Abstract

The kinetics of the oxidation of arsenite ion by platinum(IV) have been studied spectrophotometrically in basic solutions at several temperatures. The rate increases with increase in pH as well as salt concentration and dielectric constant of the medium. The empirical rate law is − d[Pt(IV)] dt =k 3[ Pt(IV)][As(III)][OH −] The rate constant is 1910±80 (dm 6 mol −2 s −1) at 25°C. The energy and entropy of activations are 42.3 (kJ mol −1) and −40.3 (J K −1 mol −1) respectively.