Silver(I) catalyzed oxidation of water with cerium(IV) in aqueous perchloric acid solutions and the reaction of cerium(IV) with silver(I) in the presence of bipyridyl

Abstract

The title reaction involves the equilibrium below and is made to go to completion by the reaction of Ag^II with water. An attempt to do this was also made by precipitating Ag^II with 2,2′-bipyridyl. Hydrogen-ion dependence shows Ce^IV+ Ag^I [graphic omitted] Ce^III+ Ag^II, Ag^II+ H²O [graphic omitted] products that CeOH³⁺ is the reactive species and the complete rate law is given by equation (i), where K₁ and K₂ are the first and second hydrolysis constants for cerium(IV). With no added cerium(III) at constant [H⁺], the rate law reduces to equation (ii). k₁ and k₂/k₃ were found to be 4.0 × 10^–3 dm³ mol^–1 s^–1 and 60 respectively at 30 °C –d [Ce^IV]/dt= [graphic omitted] (i), –d[Ce^IV]/dt=k₁[Ce^IV][Ag^I](ii) and [HClO₄]= 0.5 mol dm^–3. k″₁ was found to be 0.62 ± 0.25 dm³ mol^–1 s^–1 at 30 °C and I= 1.0 mol dm^–3. In the presence of 2,2′-bipyridyl the complex of Ag^II with this ligand is precipitated and the rate is several times larger than the forward rate of the equilibrium, perhaps owing to the more reactive Ag^I–bipyridyl complex species