Gas Pressure Sensor Monitored Iodide-Catalyzed Decomposition Kinetics of Hydrogen Peroxide

In this general chemistry laboratory experiment, the iodide-catalyzed decomposition kinetics of H2O2(aq) to H2O(l) and O2(g) is determined using the method of initial rates. The reagents (total volume 5 mL) are added to an open 25-mL test tube, and after capping the test tube, the gas pressure versus time data is collected using a datalogger and a pressure sensor. The plots, which are viewed on the datalogger in real time, are extraordinarily linear allowing for a straight-forward determination of the initial rate of reaction (slope) in 20 to 25 seconds of data collection. The reaction is first order with respect to iodide and first order with respect to hydrogen peroxide and the rate constant is 0.011040 ± 0.000013 M–1s–1 (N = 22).