Kinetics and Mechanism of Chromate Reduction with Hydrogen Peroxide in Base

[Cr^VIO₄]^2- is reduced to [Cr^V(O₂)₄]^3- by hydrogen peroxide in strongly basic media where the acid dissociation of H₂O₂ (pK_a = 11.65) is appreciable. The reaction is first order in chromium(VI) and inhibited by hydroxide. The hydrogen peroxide dependence is defined by the form of the effective pseudo-first-order rate constant:  k_eff = [H₂O₂]³/(K₁ + K₂[H₂O₂] + K₃[HO₂^-]) with K₁ = 175(43) s·M³, K₂ = 403(18) s·M², and K₃ = 1422(34) s·M². Hydrogen peroxide anion initially attacks chromate, and subsequent equilibrium steps that exchange oxo groups for three peroxo groups precede a rate-determining, one-electron, intramolecular reduction step.