Role of alkali-metal cations on the kinetics of reaction between hexacyanoferrate(III) and sulphite ions

Abstract

The kinetics of the reduction of [Fe(CN)₆]^3– by [SO₃]^2– have been investigated in presence of various alkalimetal ions. The reaction is catalysed by cations and is first order with respect to the alkali-metal-ion, [Fe(CN)₆]^3–, and [SO₃]^2– concentrations. The third-order rate constant decreases in the order Cs⁺ > Rb⁺ > K⁺ > Na⁺ > Li⁺. The activation parameters for the catalysed reaction have been determined. The rate constant varies linearly with the polarisability of the alkali-metal cation.