Question

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

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

Answer 1

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

$2NO⟶N_2{O}_2\left(Slow\right)N_2{O}_2+O_2⟶{2NO}_2\left(fast\right)$

For a multi-step process, the rate law is always determined by the slow-step in the process.

$\therefore$ $Rate=K[NO{]}^2$

Therefore, (C) is the correct answer.