The decomposition of H2O2 in aqueous solution has the experimentally determined rate law rate=k[H2O2][I−], where I− acts as a catalyst. Spectroscopic analysis shows that the concentration of I− at the beginning and end of the reaction is the same within experimental error. Which of the following best explains this observation?
a) I− is consumed in the slow elementary step and regenerated in a subsequent step, so there is no net change in its concentration.
b) I− is present in such a large excess that the small amount consumed is negligible.
c) I− is inert and does not actually participate in the reaction mechanism.
d) I− is produced by the decomposition of H2O2 at the same rate that it is consumed, keeping its concentration constant.