Kinetics of the reaction between hypochlorous acid and hexacyanoferrate(II) ion in aqueous solution

Abstract

The kinetics of the reaction of hypochlorous acid with potassium hexacyanoferrate(II) has been investigated spectrophotometrically at 25.1 °C in buffered aqueous solutions at pH 7.74 and 9.45. With HOCl in excess, the rate is given by equation (i). However, with hexacyanoferrate(II) in –d//_dt[Fe^II]=k_obs·[Fe^II](i), –d//_dt([Fe^II]₀+[Fe^II]₀–[Fe^III]_t)=k⁰([Fe^II]₀+[Fe^III]₀–[Fe^III]_t)²[HOC]//_{k*([Fe^II]0+[Fe^III]0)+(kb–k*)([Fe^II]0+[Fe^III]0–[Fe^III]t)}(ii) excess, the rate is given by equation (ii). The results obtained are interpreted in terms of a reaction mechanism in which the first stage, Fe^II+ HOCl → Cl˙+ OH^–+ Fe^III, can occur either by an irreversible or reversible process.