# Hydrogen peroxide (H_2O_2) naturally breaks down into H_2O and O_2 over time. When manganese dioxide (MnO_2) is added, the rate of this reaction increases. Based on this information, what can be hypothesized?

That $M n {O}_{2}$ catalyzes the decomposition of hydrogen peroxide.
${H}_{2} {O}_{2} \rightarrow {H}_{2} O + \frac{1}{2} {O}_{2}$
This reaction has a measurable rate, and in the presence of $M n {O}_{2}$, this rate is faster. Since, by definition, a catalyst modifies reaction rate, the added oxide has acted as a catalyst, and provided an alternative reaction pathway.