Reaction of FD&C Blue 1 with Sodium Percarbonate: Multiple Kinetics Methods Using an Inexpensive Light Meter

In selecting from a repertoire of traditional kinetics experiments, an instructor often has to choose among having students gain experience with the graphical method, the method of initial rates, or a temperature-dependent experiment in which students construct an Arrhenius plot. This paper presents an environmentally friendly bleaching reaction between the dye FD&C Blue 1 and a nonchlorinated bleach alternative, sodium percarbonate, which goes to completion within 15 min and can be monitored with an inexpensive light meter. The fast time scale of the reaction allows students to use the graphical method along with the method of initial rates to determine the overall rate law, as well as collect data for an Arrhenius plot, potentially within a 3 h laboratory period. Students can generate an Arrhenius plot quickly and inexpensively by detecting the extent of reaction in a beaker using a desk lamp, filter, and light meter, eliminating the need for spectrophotometer access, a jacketed cell, and a heated circulating bath. Performing all three types of kinetics experiments with one simple reaction in one or two laboratory periods allows students to see how the methods are interrelated and complementary.