2 CO (g) + O2 (g) --> 2 CO2 (g)
The mechanism below has been proposed for this reaction;
(slow) O2 + CO --> CO2 + O
(fast) O + CO --> CO2
Based on this mechanism what is the rate law for this reaction?
To determine the rate law for a reaction based on a proposed mechanism, we need to identify the rate-determining step. The rate-determining step is the slowest step in the overall reaction, and its kinetics will determine the rate law.
In this mechanism, the slow step is:
O2 + CO --> CO2 + O
Based on the stoichiometry of this step, we can see that the reaction is first-order with respect to O2 and CO. Therefore, the rate law for this step is:
Rate = k1[O2][CO]
Now, since the slow step is the rate-determining step, the overall rate law for the reaction is determined by this step. The fast step does not affect the overall rate law because it occurs much faster.
Thus, the rate law for the reaction is:
Rate = k1[O2][CO]
where k1 is the rate constant for the slow step.