Chapter 22, Problem 79A

Interpretation Introduction

Interpretation:

The rate determining step needs to be explained.

Concept introduction:

For a chemical reaction, the slowest step in the mechanism is rate determining step.

Explanation of Solution

In a chemical reaction, the slowest step is the rate determining step. This step determines the rate of the reaction. If a chemical reaction takes place in the step by step process in which reactants are converted to products, the slowest step is the rate determining step. The slow step is characterized by the high activation energy.

For example:

The reaction of nitrogen dioxide gas and carbon monoxide gas results in the formation of nitrogen oxide gas and carbon dioxide gas.

${\text{NO}}_{\text{2}}\left(g\right)+\text{CO}\left(g\right)\to \text{NO}\left(g\right)+{\text{CO}}_{\text{2}}\left(g\right)$

The mechanism of the reaction can be represented as follows:

$\begin{array}{l}{\text{Step 1: NO}}_{\text{2}}\left(g\right)+{\text{NO}}_{\text{2}}\left(g\right)\stackrel{K_1}{\to }\text{NO}\left(g\right)+{\text{NO}}_3\left(g\right)\text{ Slow}\\ {\text{Step 2: NO}}_3\left(g\right)\text{+CO}\left(g\right)\to {\text{NO}}_{\text{2}}\left(g\right)+{\text{CO}}_{\text{2}}\left(g\right)\text{ Fast}\end{array}$

Here, the first step is rate determining step.