The use of a catalyst in the decomposition of hydrogen peroxide H2O2 into water H2O and oxygen O2 significantly affects the reaction rate and mechanism.1. Reaction rate: A catalyst increases the reaction rate by providing an alternative reaction pathway with a lower activation energy. This allows more reactant molecules to have sufficient energy to overcome the activation energy barrier, leading to a faster reaction. In the case of hydrogen peroxide decomposition, catalysts such as manganese dioxide MnO2 , potassium iodide KI , or catalase an enzyme can be used to speed up the reaction.2. Reaction mechanism: The presence of a catalyst can change the reaction mechanism by introducing new intermediate steps. These steps involve the formation of temporary bonds between the reactants and the catalyst, which helps to lower the activation energy required for the reaction to proceed. For example, when using manganese dioxide as a catalyst, the following reaction mechanism is proposed:Step 1: H2O2 aq + MnO2 s H2O l + O2 g + MnO2 s Step 2: H2O2 aq + MnO2 s H2O l + O2 g + MnO2 s In this mechanism, the manganese dioxide catalyst remains unchanged throughout the reaction, as it is regenerated in each step. This is a characteristic feature of catalysts they are not consumed in the overall reaction.In summary, the use of a catalyst in the decomposition of hydrogen peroxide into water and oxygen significantly increases the reaction rate by providing an alternative reaction pathway with a lower activation energy and may also change the reaction mechanism by introducing new intermediate steps.