A Colorful Catalysis Demonstration

A simple, yet colorful, homogeneous catalysis demonstration is reported. When concentrated H2O2 is added to a yellow-orange aqueous solution of Fe3+, the solution turns black in color. After a brief induction period, exothermic decomposition of H2O2 ensues with the evolution of oxygen gas. As the reaction subsides, the solution returns to the original yellow-orange color. These color changes demonstrate one of the most important (and often most misunderstood by first-year students) concepts of catalysis—although a catalyst may be altered as it participates in a reaction, it is not consumed.