Kinetics of oxidation-reduction reactions between elements of Groups V and VII. Part I. Bismuth(V) with halide ions and other reductants

Abstract

The oxidations of the ions I–, Br–, Cl–, SCN–, Tl+. and IrCl63– by bismuth(V) in perchloric acid solution all obey the rate expression –d[BiV]/dt=k[BiV], where k= 161·4 ± 8·0 s–1 at [H+]= 0·5M, I= 2·0M, and t= 25 °C. Rates of reaction are practically independent of [H+] in the range 0·5–2·0M. Measurements at four different temperatures give Ea= 7·1 ± 0·3 kJ mol–1 and ΔS‡=–187 ± 1 J K–1 mol–1. Mechanisms consistent with this data are discussed and that involving (i) as the rate-determining step is preferred. [graphic omitted] → [graphic omitted] + 2H+(i) Potentiometric titrations give E0= 2·03 ± 0·17 V for the half-cell reaction BiV+ 2e → BiIII at [H+]= 0·5M, I= 2·0M, and t= 25 °C.