Chapter 16.3, Problem 20PP

Interpretation Introduction

Interpretation:

The rate law for the reaction $2\text{NO}\text{(}g\text{)}\text{+}{\text{O}}_2(g)\to 2{\text{NO}}_{\text{2}}(g)$ needs to be determined.

Concept introduction:

The relationship between rate of a chemical reaction and concentration of reactants is expressed by rate law. Rate law is written using the concentration of reactants.

Answer to Problem 20PP

Rate law for the reaction is, $\text{Rate}=k{[\text{NO}]}^2[{\text{O}}_{\text{2}}]$

Explanation of Solution

For an one step reaction such as $a\text{A}\to b\text{B}$, rate law is expressed by the product of concentration of reactants each raised to a power which is experimentally determined and the rate constant k.

$\text{Rate=}k{[\text{A}]}^a$

The given reaction is $2\text{NO}\text{(}g\text{)}\text{+}{\text{O}}_2(g)\to 2{\text{NO}}_{\text{2}}(g)$, The order of ${\text{O}}_2$ is 1 and the overall order is 3. So, the order of NO is 2. Hence, rate law is,

$\text{Rate}=k{[\text{NO}]}^2[{\text{O}}_{\text{2}}]$

Conclusion

The coefficient of the reactant in a reaction indicates the order of the reactant.