Chapter 11.7, Problem 11.11E

Interpretation Introduction

Interpretation:

The rate law for the step $2$ of the mechanism for the reaction of hydrogen peroxide and iodide ion has to be written.  The overall rate is unaffected by the rate of step $2$, the reason for this has to be given.

Concept Introduction:

The relationship between rate and initial concentration of reactant is described by rate law.  It is an experimentally determined equation and cannot be found out theoretically from the stoichiometry of the reactants and products.

  $rate=k{\left[concentrationofthereac\tan t\right]}^m$

Where, $k$ is the rate constant and $m$ is the order of the reaction.

The oxidation reaction of iodide ion by hydrogen peroxide in acidic solution is given below.  It is a three step process.

Step $1$:

  $HOOH+I^{-}\stackrel{slow}{\to }O{H}^{-}+HOI$

Step $2$:

  $HOI+I^{-}\stackrel{fast}{\to }O{H}^{-}+I_2$

Step $3$:

  $O{H}^{-}+H^{+}\stackrel{fast}{\to }{H}_{2}O$

In a multistep reaction, the overall rate of the reaction depends on the rate of the slowest step.