When manganese (IV) oxide is added to hydrogen peroxide, oxygen and water are produced but there is no change in the manganese oxide. Note: the reaction rate 1g of manganese oxide is added to 100cm^3 of a solution of hydrogen peroxide.
If the following changes are made to the experiment, how will the reaction rate change?
Use 100cm^3 of the original hydrogen peroxide but grind the 1g of manganese oxide into a fine powder.
In this reaction, manganese oxide is the catalyst and catalyses the decomposition of hydrogen peroxide. Chemically this reaction can be written as:
`2H_2O_2 -> O_2 + 2H_2O`
MnO2 does not show itself in the equation because it is a catalyst. Catalysts typically act by either providing a lower energy pathway or are first consumed and then produced during the reaction, thus their total quantity remains unaffected.
If instead of using a solid catalyst lump, we finely grind it, the surface area of catalyst particles will increase and will speed up the reaction. This happens because the greater surface area of catalyst increases the chances of reactant particles colliding with it (for formation of catalyst-reactant intermediate which forms products and releases catalyst back).
Hence the finely divided MnO2 particles will speed up the breakdown of hydrogen peroxide.