Chemistry - Chemical Kinetics Question with Solution | TestHub

The rate of the reaction is determined by the slowest step, which is the rate-determining step.

From step (ii), the rate equation is:
$r=k[{\text{NOBr}}_2][\text{NO}]$

Since ${\text{NOBr}}_2$ is an intermediate, its concentration must be expressed in terms of the reactants. Assuming step (i) is a fast equilibrium:
$K_{eq}=\frac{[{\text{NOBr}}_2]}{[\text{NO}][{\text{Br}}_2]}$

$[{\text{NOBr}}_2]=K_{eq}[\text{NO}][{\text{Br}}_2]$

Substituting this into the rate equation:
$r=k(K_{eq}[\text{NO}][{\text{Br}}_2])[\text{NO}]$

$r=k^{\prime }[\text{NO}{]}^2[{\text{Br}}_2]$ where $k^{\prime }=k{K}_{eq}$

Answer: $r=k^{\prime }[\text{NO}{]}^2[{\text{Br}}_2]$