A Microscale Approach to Chemical Kinetics in the General Chemistry Laboratory: The Potassium Iodide Hydrogen Peroxide Iodine-Clock Reaction

A microscale laboratory for teaching chemical kinetics utilizing the iodine clock reaction is described. Plastic pipets, 3 mL volume, are used to store and deliver precise drops of reagents and the reaction is run in a 24 well plastic tray using a total 60 drops of reagents. With this procedure, students determine the rate of reaction and the order of reaction as a function of iodide ion concentration or hydrogen peroxide concentration. Six reaction concentrations are run concurrently in about an hour. The students also calculate the value of the rate constant and determine the concentration of an unknown iodide ion sample. The procedure has been adopted to run at a lower temperature to determine the energy of activation. The experiment teaches the principles of chemical kinetics to first-year college students and can also be used in second-year or advanced-placement high school chemistry classes.