Chapter 18, Problem 129CP

(a)

Interpretation Introduction

Interpretation: The overall balance chemical reaction for the ozone destruction needs to be determined.

  

Concept Introduction:

Chemical kinetic is the branch of chemistry that deals with kinetic or rate of a chemical reaction. The rate of reaction can be defined as the change in the concentration of reactant and product with time. The rate of reaction mainly depends on the activation energy.

In a chemical reaction to be occurred; two most important requirements are activation energy to reactant molecule and correct orientation of reactant molecules to colloid and form product.

Answer to Problem 129CP

  ${\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}$

Explanation of Solution

On the basis of number of steps in a chemical reaction, the reactions can be classified as elementary reactions and multi-step reaction. The elementary step of a chemical reaction can be defined as the primary step of the reaction which comprise together to show the complete conversion of a reactant to product in the multi-step reaction.

The given ball and stick model for the chemical reaction is:

  

Hence the steps of the given reaction can be written as:

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

(b)

Interpretation Introduction

Interpretation: The species which act as catalyst for the ozone destruction needs to be determined.

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

Concept Introduction:

Chemical kinetic is the branch of chemistry that deals with kinetic or rate of a chemical reaction. The rate of reaction can be defined as the change in the concentration of reactant and product with time. The rate of reaction mainly depends on the activation energy.

In a chemical reaction to be occurred; two most important requirements are activation energy to reactant molecule and correct orientation of reactant molecules to colloid and form product.

Answer to Problem 129CP

NO must be catalyst for the given reaction.

Explanation of Solution

Catalyst can be defined as the substance which enhance the rate of reaction and again regenerate at the end of reaction.

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

In the given reaction NO involves in step-1 and again regenerate in step-2 therefore it is not part of overall reaction. Hence NO must be catalyst for the given reaction.

(c)

Interpretation Introduction

Interpretation: The species which act as intermediate for the ozone destruction needs to be determined.

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

Concept Introduction:

Chemical kinetic is the branch of chemistry that deals with kinetic or rate of a chemical reaction. The rate of reaction can be defined as the change in the concentration of reactant and product with time. The rate of reaction mainly depends on the activation energy.

In a chemical reaction to be occurred; two most important requirements are activation energy to reactant molecule and correct orientation of reactant molecules to colloid and form product.

Answer to Problem 129CP

  ${\text{NO}}_{\text{2}}$ must be intermediate for the given reaction.

Explanation of Solution

The species which is formed during the reaction and will convert to product at the end of reaction is called as intermediate.

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

In the given reaction ${\text{NO}}_{\text{2}}$ molecules form in step-1 and again consume in step-2 therefore it is not part of overall reaction. Hence ${\text{NO}}_{\text{2}}$ must be intermediate for the given reaction.

(d)

Interpretation Introduction

Interpretation: The rate law for the given ozone destruction reaction if the step-1 is slow and step-2 is fast step needs to be determined.

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

Concept Introduction:

Chemical kinetic is the branch of chemistry that deals with kinetic or rate of a chemical reaction. The rate of reaction can be defined as the change in the concentration of reactant and product with time. The rate of reaction mainly depends on the activation energy.

In a chemical reaction to be occurred; two most important requirements are activation energy to reactant molecule and correct orientation of reactant molecules to colloid and form product.

Answer to Problem 129CP

  ${\text{Rate = k [O}}_{\text{3}}\text{] [NO]}$

Explanation of Solution

Given:

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\text{ (slow)}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\text{ (fast)}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

In the given reaction, the step-1 is slow step and step-2 is fast step therefore the rate law will be determined with the help of step-1. In step-1; O3 and NO take part therefore the rate law can be written as:

  ${\text{Rate = k [O}}_{\text{3}}\text{] [NO]}$

(e)

Interpretation Introduction

Interpretation: The two step mechanism with second step and overall balance reaction for the rate law for ozone destruction by chlorine which are formed by reaction of Freons with light needs to be determined.

  ${\text{Cl}}_{\text{(g)}}{\text{ + O}}_{\text{3(g) }}\stackrel{}{\to }{\text{ClO}}_{\text{(g) }}\text{+ Cl}$

Concept Introduction:

Chemical kinetic is the branch of chemistry that deals with kinetic or rate of a chemical reaction. The rate of reaction can be defined as the change in the concentration of reactant and product with time. The rate of reaction mainly depends on the activation energy.

In a chemical reaction to be occurred; two most important requirements are activation energy to reactant molecule and correct orientation of reactant molecules to colloid and form product.

Answer to Problem 129CP

  $\begin{array}{l}{\text{O}}_{{\text{3}}_{\text{(g)}}}{\text{ + Cl}}_{\text{(g)}}\stackrel{}{\to }{\text{ O}}_{{\text{2}}_{\text{(g)}}}{\text{+ ClO}}_{\text{(g)}}\text{ (slow)}\\ {\text{ClO}}_{\text{(g)}}{\text{+ [O]}}_{\text{(g)}}\stackrel{}{\to }{\text{ O}}_{{\text{2}}_{\text{(g)}}}{\text{+ Cl}}_{\text{(g)}}\text{ (fast)}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{{\text{3}}_{\text{(g)}}}{\text{ +[O]}}_{\text{(g)}}\stackrel{}{\to }{\text{2 O}}_{{\text{2}}_{\text{(g)}}}\text{(overall reaction)}\end{array}$

Explanation of Solution

The destruction of ozone with NO is given below:

  $\begin{array}{l}{\text{O}}_{\text{3}}\text{ + NO }\stackrel{}{\to }{\text{NO}}_{\text{2}}{\text{+O}}_{\text{2}}\text{ (slow)}\\ {\text{NO}}_{\text{2}}\text{+[O]}\stackrel{}{\to }{\text{NO+O}}_{\text{2}}\text{ (fast)}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{\text{3}}\text{ +[O]}\stackrel{}{\to }{\text{2O}}_{\text{2}}\text{(overall reaction)}\end{array}$

Freons can form active Cl atoms in the presence of light which can further react with ozone to form oxygen gas. The mechanism can be written as:

  $\begin{array}{l}{\text{O}}_{{\text{3}}_{\text{(g)}}}{\text{ + Cl}}_{\text{(g)}}\stackrel{}{\to }{\text{ O}}_{{\text{2}}_{\text{(g)}}}{\text{+ ClO}}_{\text{(g)}}\text{ (slow)}\\ {\text{ClO}}_{\text{(g)}}{\text{+ [O]}}_{\text{(g)}}\stackrel{}{\to }{\text{ O}}_{{\text{2}}_{\text{(g)}}}{\text{+ Cl}}_{\text{(g)}}\text{ (fast)}\\ \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_}\\ {\text{O}}_{{\text{3}}_{\text{(g)}}}{\text{ +[O]}}_{\text{(g)}}\stackrel{}{\to }{\text{2 O}}_{{\text{2}}_{\text{(g)}}}\text{(overall reaction)}\end{array}$