The presence of a catalyst affects the rate of reaction between hydrogen peroxide H2O2 and potassium iodide KI by providing an alternative reaction pathway with a lower activation energy. This allows the reaction to proceed more quickly, increasing the rate of reaction.In the reaction between hydrogen peroxide and potassium iodide, the iodide ions I- act as a catalyst. The reaction can be represented as follows:H2O2 aq + 2I^- aq 2H2O l + I2 aq The catalyst, in this case, the iodide ions, is not consumed in the reaction and can be used repeatedly to catalyze the reaction.To compare the reaction rates in the presence and absence of a catalyst, we can use kinetic data obtained from experiments. This can be done by measuring the rate of disappearance of hydrogen peroxide or the rate of appearance of iodine in both catalyzed and uncatalyzed reactions.One common method to measure the rate of reaction is by monitoring the change in absorbance of a solution using a spectrophotometer. In this case, the appearance of iodine I2 can be monitored as it has a characteristic absorbance at a specific wavelength.By plotting the absorbance versus time, we can determine the initial rate of the reaction for both the catalyzed and uncatalyzed reactions. The initial rate is the slope of the tangent to the curve at the beginning of the reaction t=0 . Comparing the initial rates will give us an idea of how much faster the reaction is in the presence of the catalyst.Another method to compare the reaction rates is by measuring the time it takes for the reaction to reach a certain percentage of completion e.g., 50% completion in both the catalyzed and uncatalyzed reactions. The ratio of these times can give an indication of the effect of the catalyst on the reaction rate.In summary, the presence of a catalyst, such as iodide ions, increases the rate of reaction between hydrogen peroxide and potassium iodide by lowering the activation energy. Kinetic data, such as absorbance measurements or time to reach a certain percentage of completion, can be used to compare the reaction rates in the presence and absence of a catalyst.