When free \(\ce{Cl(g)}\) atoms encounter \(\ce{O3(g)}\) molecules in the upper atmosphere, the following reaction mechanism is proposed to occur.

$$ \begin{array}{c c c} \ce{Cl(g) + O3(g) -> ClO(g) + O2(g)} & \textit{slow step} & \\ \ce{ClO(g) + O3(g) -> Cl(g) + 2O2(g)} & \textit{fast step} & \\ \hline \ce{2O3(g) -> 3O2(g)} & \textit{overall reaction} & \Delta H=\pu{-285 kJ/mol_{rxn}} \end{array} $$

Which of the following rate laws for the overall reaction corresponds to the proposed mechanism?

Summary Submit Skip Question

The rate law can be determined from the slowest step, which is known as the rate-determining step.

$$ \ce{1Cl(g) + 1O3(g) -> ClO(g) + O2(g)} $$

In this step, 1 molecule of chlorine and 1 molecule of ozone react. We can use the coefficients of the reactants to write the rate law.

\( \text{Rate}=k[\ce{Cl}]^1[\ce{O3}]^1\)