Kinetics of oxidation of antimony(III) by cerium(IV) in media containing perchloric acid

Abstract

The oxidation of antimony(III) by cerium(IV) in perchloric acid medium follows the rate law (i). k₂ and k₃ were –d[Ce^IV]//_dt=2[Ce^IV][Sb^III](k₂[H⁺]+k₃K₂)//_[H⁺]+K2(i) found to be 35 and 300 l. mole^–1 sec.^–1 respectively at 2M ionic strength and 25°. K₂ is the second hydrolysis constant of ceric ion. The active species are assumed to be the hydrolytic species of Ce^IV and SbO⁺, based on the effect of hydrogen ion concentration and spectrophotometric measurements. An atom transfer mechanism is suggested. The effect of the bridging atoms is in the order Br^– > Cl^– > OH^– > HSO₄^–. Because the reaction of Ce^IV with Cl^– is slower than that of Ce^IV with Sb^III in presence of chloride, it is concluded that the acceleration of rate by Cl^– is not a case of redox catalysis.