Content area
Full Text
Most chemistry students know that a catalyst is a substance that causes the rate of a reaction to increase and is regenerated at the end of the reaction, but they are not always certain how or why a catalyst works. We believe that this is because many beginning texts simply state that a catalyst provides a new pathway for the reaction, one with a lower activation energy (1). This, of course, need not be the case, since any additional pathway will lead to an increase in rate even if it has a higher activation energy. This is because two reactions running simultaneously will always have a combined rate that is faster than one alone. Too often, authors fail to emphasize that the original reaction is still taking place and that, depending upon conditions, it is possible for this original reaction to proceed at a faster rate than the catalyzed reaction. This situation is purposefully created by the conditions chosen for this experiment.
The Experiment
Results and Discussion
The First thing students notice is that McO^sub 4^^sup 2^- acts as a catalyst for the reaction, since it (1) clearly speeds up the rate Of 12 production and (ii) must also be regenerated, since it is present in far less than a stoichiometric amount. But very much to the students' surprise, when they subtract the noncatalyzed rate from the overall rate...