The complex [Fe(S2O3)]+
is purple and the starch-pentaiodide complex is blue.
Note that equation (2) presents a reversible reaction which occurs in the
reaction mixture but is not included in the clock reaction scheme (1) given
above.
Explain how the set of chemical changes (2–5) is responsible for the clock
effect in this reaction. Which of steps (2–5) is the slow step, and why is this
so? Identify the limiting reagent.