A kinetic study of the displacement reaction between nickel(II) and zinc-ethylenediaminetetraacetate by a radiometric method

A radiometric study of the kinetics of the displacement reaction between nickel(II) and⁶⁵Zn-labeled zinc salt of ethylenediaminetetraacetic acid, which was previously used by the authors for the analysis of trace quantities of nickel, has been carried out under varying conditions of temperature, pH etc. The above reaction was confirmed to be first order with respect to both Ni²⁺ and to^*ZnEDTA. The overall reaction rate constant, k_f, has been shown to be inversely proportional to the concentration of Zn²⁺ and directly proportional to the concentration of H⁺. From the dependence of the rate constant on the concentration of Zn²⁺ and H⁺ a three-step mechanism is proposed for the above reaction. The values for E_a, ΔH^‡, ΔG^‡ and ΔS^‡ for the overall reaction have been computed from the experimental data.