Another way to catalyze the decomposition of H2O2 is to add a few drops of a solution containing iodide ion (I–): 2 upper H subscript 2 upper O subscript 2 (a q) right arrow with upper I superscript minus (a q) above it, 2 upper H subscript 2 upper O (l) plus upper O subscript 2 (g). ✔ homogeneousX heterogeneous