A laboratory exercise has recently been reported in which the
students use the initial rates method based on the clock reaction approach to deduce
the rate law and propose a reaction mechanism for the oxidation of iodide by
iron(III) ions. The same approach is used in the exercise proposed herein; the
students determine the dependence of the reaction rate on ionic strength and
temperature in a straightforward manner. The previously proposed mechanism is
further supported by the results, the rate-determining step is identified, and the
activation parameters Ea, Δ⧧H, and Δ⧧S are determined for the overall reaction of
the first two steps of the mechanism. The significance of such kinetic studies in
elaborating reaction mechanisms is clearly demonstrated to the students.