Chapter 17, Problem 17E.3ST

Interpretation Introduction

Interpretation:

The pre-equilibrium mechanism in the given reaction results in an overall third-order reaction has to be shown.

Concept introduction:

Pre-equilibrium: Consider a reaction that is more complicated mechanism in which an intermediate I reach equilibrium with the reactants A and B:

  $A+B\underset{\begin{array}{l}\\ k_a^{\text{'}}\end{array}}{\overset{k_a}{\rightleftharpoons }}I\stackrel{k_b}{\to }P$.

This above scheme involves a pre-equilibrium, in which an intermediate is in equilibrium with the reactants. A pre-equilibrium arises when the rate of decay of the intermediate back into reactants is much faster than the rate at which it forms products; the condition is satisfied if $k_a^{\text{'}}>>k_b.$

Rate law or rate equation: The relationship between the reactant concentrations and reaction rate is expressed by an equation.

  $\text{aA + bB}\to x\text{X}$.

Rate of the reaction ${\text{ = k [A]}}^{\text{m}}{\text{[B]}}^{\text{n}}$.

Total order of the reaction $\text{ = }\left(\text{m + n}\right)$.