Kinetic studies of the bromate-iodide reaction; catalysis by vanadate (V) ion

Abstract

The rate laws, v = K0(H+)2 (BrO3-) (I-) and v = K0(H+)2 (BrO3-) (I-) + K6(H+) (BrO3-) (I-) (Mo(VI)), were K0 = 50.26M-3 sec-1 and K6 = (3.1 Ŧ 0.l).10 4 M-3sec-1 , have been confirmed for the uncatalyzed and molybdate (VI) catalyzed bromate-iodide reactions respectively, over concentration ranges greater than those employed by earlier workers. The rotating Pt disc electrode technique has been used throughout to monitor reaction rates. Kinetic studies on the vanadium (V) catalyzed bromate-iodide reaction have been made. The rate law, v = K0(H+)2(BrO3-) (I-) + K6(BrO3-).f[(H+),(V(V))], where f[(H+), (V(V))] represents an incompletely evaluated interdependence on the (H+) and vanadate (V) ion concentrations, has been observed. All rate studies have been performed at 25°C and 1.00M total ionic strength, in KNO3 medium. Electrochemical interferences, observed for both the molybdate (VI) and vanadate (V) catalyzed reactions, in strong acid conditions, have been studied and partly explained.