An Approximate Expression for the Reaction Rate of the Clock-Reaction

Abstract

This work is to study the clock-reaction for establishing an expression of its reaction rate through a simple procedure. We tried to define the average reaction rate as a valid expression of the reaction rate in the clock-reaction system. The average reaction rate, Va, in potassium iodate-sodium sulfite-sulfuric acid system is expressed as follows; Va=－[SO₃^2－]₀ / Δt, where [SO₃^2－]₀ and Δt are the initial concentration of sulfite ion and the induction time of this reaction, respectively. According to this definition of the rate of reaction, the rate equation of the above mentioned reaction system is derived from its experimental results as follows; Va = K [IO₃^－]² [SO₃^2－] [H^＋]², where K is the rate constant. The assumption that proton catalyzes this reaction in the form of [H^＋]² leads us to the following successive reaction path which consists of only the chemical species already identified by the various studies of this reaction system; 2IO₃^－ + HSO₃^－　∧→　IO^－ + IO₂^－ + SO₄^2－ + H⁺　IO^－ + HSO₃^－　→　I^－ + H⁺ + SO₄^2－　IO₂^－ + 2HSO₃^－　―　I^－ + 2H⁺ + 2SO₄^2－