Which of the following could not be rate determining step?

The correct answer is option 2. \(O_3 ⇌ O_2 + O\).

Let us analyze why option 2 \(O_3 ⇌ O_2 + O\) couldn't be the rate-determining step:

The given reaction represents the dissociation of ozone (\(O_3\)) into oxygen gas (\(O_2\)) and an oxygen atom (\(O\)). This reaction is reversible, meaning it can proceed in both the forward and reverse directions.

The rate-determining step in a reaction is typically the slowest step that determines the overall rate of the reaction. In the case of a reversible reaction like the dissociation of ozone, both the forward and reverse reactions could potentially be the rate-determining step depending on the reaction conditions.

However, since the reaction is reversible and involves the breaking of a relatively weak bond in ozone (\(O_3\)), it's unlikely that this step would be the rate-determining step. The dissociation of ozone is generally a fast process compared to other chemical reactions, so it's less likely to be the slowest step determining the overall rate of the reaction.

Therefore, the dissociation of ozone (\(O_3 ⇌ O_2 + O\)) is unlikely to be the rate-determining step compared to the other reactions provided.