Question

Below is a proposed two-step mechanism for the decomposition of hydrogen peroxide: h2o2(aq) + br−(aq) → h2o(ℓ) + bro−(aq) slow bro−(aq) + h2o2(aq) → h2o(ℓ) + o2(g) + br−(aq) fast is this homogeneous or heterogeneous catalysis? also identify the catalyst in the mechanism.

Answer 1

Answer : This is homogeneous catalysis. Br⁻ is behaving as a catalyst

Explanation :

Let us write down the given reactions.

$H_{2}O_{2} (aq) + Br^- (aq) \rightarrow H_{2}O (l) + BrO^{-} (aq)$ .....Slow

$BrO^{-} (aq) + H_{2}O_{2} (aq) \rightarrow H_{2}O (l) + O_{2} (g) + Br^{-}$ .....Fast

A catalyst is defined as a substance that increases the rate of the reaction.

A catalyst takes part in the reaction by reacting with the reactants to form an intermediate. But it is regenerated at the end of the reaction.

If we take a look at the above reactions, we can see that bromide ion Br⁻ is reacting with H₂O₂ to form an intermediate BrO⁻. It is also getting regenerated back at the end. That means Br⁻ is behaving as a catalyst.

We can also see that the reactant and the catalyst are in the same phase which is aqueous phase. Therefore the reaction is homogeneous.

A homogeneous reaction is the one where the reactants and the catalyst are in the same phase.