4. When Fe(NO3)3 is added to water, the following dissociation reaction occurs:
Fe(NO3)3 →
Fe3+ + 3 NO3
The Fe3+ is able to move freely through the H2O2 solution and catalyze the decomposition reaction.
Similarly, when Na3PO4 is added to water the following dissociation reaction occurs:
Na3PO4 → 3 Na+ + PO-.
When Fe3+ is combined with POS, an insoluble precipitate of FePO4(s) forms:
Fe3+ + POS- →
FePO4(s).
Why is Na3POs expected to act as an inhibitor for the catalyzed decomposition of H2O2 by Fe3+?