The reaction mechanism affects the reaction rate in the decomposition of hydrogen peroxide H2O2 catalyzed by iodide ions I- by providing an alternative pathway with lower activation energy, which in turn increases the rate of the reaction.The decomposition of hydrogen peroxide can be represented by the following reaction:2H2O2 2H2O + O2In the presence of iodide ions, the reaction mechanism involves two elementary steps:1. H2O2 + I- HOI + H2O slow step 2. H2O2 + HOI H2O + O2 + I- fast step In the first step, iodide ions act as a catalyst by reacting with hydrogen peroxide to form hypoiodous acid HOI and water. This step is the rate-determining step as it is slower than the second step. The activation energy for this step is lower than the activation energy for the uncatalyzed decomposition of hydrogen peroxide, which allows the reaction to proceed more quickly.In the second step, hydrogen peroxide reacts with hypoiodous acid to form water, oxygen, and iodide ions. This step is faster than the first step, and the iodide ions are regenerated, allowing them to participate in the reaction again. This is a key feature of catalysts, as they are not consumed in the overall reaction.The presence of iodide ions in the reaction mechanism provides an alternative pathway with lower activation energy, which increases the rate of the reaction. The rate of the reaction depends on the concentration of the reactants and the rate constant, which is influenced by the activation energy. By lowering the activation energy, the rate constant increases, and the reaction rate increases as well.