Influence of electrolytic dissociation upon rates of reactions. Part VIII. Acceleration of the reaction between chromium(II) and the chloropenta-amminechromium(III) complex by sulphate ion

Abstract

The rate of reaction between Cr²⁺ and Cr(NH₃)₅Cl²⁺ has been studied over a range of ionic strength at 25 °C. The rate constant at zero ionic strength was found to be 2·48 × 10^–3 l mol^–1 s^–1. By using solutions of sodium sulphamate (which is redox-inert) buffered at pH 4·3, it was shown that addition of sulphate ions accelerates the reaction. This is attributed to the formation of kinetically active reactant–sulphate ion-pairs and the rate constant for the reaction of CrSO₄ with Cr(NH₃)₅Cl²⁺ is calculated to be 0·068 l mol^–1 s^–1.