Catalysts Practice Test

The reaction $\text{SO}_2(g)+\text{NO}_2(g)\rightarrow \text{SO}_3(g)+\text{NO}(g)$ is studied in a sealed container at constant temperature. In a second trial, a small amount of $\text{NO}(g)$ is added as a catalyst and is regenerated during the reaction. The overall reactants and products remain the same, and the catalyst is not consumed.

Which statement best explains the increased rate in the presence of the catalyst?

Aqueous iodide reacts with hydrogen peroxide in acidic solution: $\text{H}_2\text{O}_2(aq)+2\text{I}^-(aq)+2\text{H}^+(aq)\rightarrow \text{I}_2(aq)+2\text{H}_2\text{O}(l)$. Two experiments use the same initial concentrations and temperature. In Experiment 2, a small amount of $\text{Fe}^{3+}(aq)$ is added and is regenerated during the reaction (not consumed overall). The reactants and products are the same in both experiments.

Why does adding $\text{Fe}^{3+}(aq)$ increase the reaction rate?