The reaction $2 \mathrm{NO}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \rightarrow 2 \mathrm{NOCl}(g)$ obeys
the rate law, rate $=k[\mathrm{NO}]^{2}\left[\mathrm{Cl}_{2}\right]$. The following mechanism has been proposed for this reaction:
$$
\begin{array}{r}
\mathrm{NO}(g)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{NOCl}_{2}(g) \\
\mathrm{NOCl}_{2}(g)+\mathrm{NO}(g) \rightarrow \rightarrow 2 \mathrm{NOCl}(g)
\end{array}
$$
(a) What would the rate law be if the first step were rate determining? (b) Based on the observed rate law, what can we conclude about the relative rates of the two steps?