Question

For the following mechanisms, which of the following is the correct rate law?
$NO+NO\to N_2{O}_2\left(slow\right)$
$N_2{O}_2+O_2\to 2N{O}_2\left(fast\right)$

• A. $Rate=k\left[NO{]}^2\right[O_2]$
• B. $Rate=k\left[N_2{O}_2\right]\left[O_2\right]$
• C. $Rate=k\left[N_2{O}_2\right]$
• D. $Rate=k[NO{]}^2$

Answer 1

The correct option is D $Rate=k[NO{]}^2$

For a complex reaction, the rate law is determined by the slow-step reaction.

The slow-step reaction is $NO+NO⟶N_2{O}_2$

$\therefore$ Rate$=k\left[NO\right]\left[NO\right]$

$\therefore$ Rate$=k{\left[NO\right]}^2$

Therefore, option $\left(D\right)$ is the correct answer.