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 the reaction, we need to identify the slow step in the proposed mechanism, as the rate of the overall reaction is determined by the rate of the slowest step.

In this case, the slow step is the first step: O2 + CO --> CO2 + O

Based on this slow step, we can write the rate law as:
Rate = k[O2][CO]

Where:
- Rate is the rate of the reaction
- k is the rate constant
- [O2] is the concentration of O2
- [CO] is the concentration of CO

Therefore, the rate law for this reaction is Rate = k[O2][CO].

To determine the rate law for a reaction based on its mechanism, we need to examine the rate-determining step, which is the slowest step in the reaction mechanism. In this case, the slow step is:

O2 + CO --> CO2 + O

The rate of this step is determined by the concentration of O2 and CO, according to the stoichiometry of the reaction. Therefore, we can write the rate law for this step as:

Rate = k1[O2][CO]

Where k1 is the rate constant for the slow step.

However, it's important to note that the fast step, O + CO --> CO2, is a fast equilibrium step that quickly reaches equilibrium based on the concentrations of O and CO. Therefore, the concentration of O is constant and can be considered as a constant in the rate law.

So, the rate law for the overall reaction, based on the proposed mechanism, is:

Rate = k1[O2][CO]

Where k1 is the rate constant for the slow step, and the concentration of O is considered constant.