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Chemistry · Ch 9 — Hydrogen

Chemical Properties

9.7.4

Chemical Properties

Dual Oxidising and Reducing Behaviour

Hydrogen peroxide is unusual in that it can act as either an oxidising agent or a reducing agent, in both acidic and basic media, because the oxygen in H2O2H_2O_2 sits at an intermediate oxidation state (−1) between O2−O^{2-} (as in water) and O2O_2 (oxidation state 0).

Oxidising action, acidic medium:

2Fe2+(aq)+2H+(aq)+H2O2(aq)→2Fe3+(aq)+2H2O(l)2Fe^{2+}(aq) + 2H^+(aq) + H_2O_2(aq) \rightarrow 2Fe^{3+}(aq) + 2H_2O(l)

PbS(s)+4H2O2(aq)→PbSO4(s)+4H2O(l)PbS(s) + 4H_2O_2(aq) \rightarrow PbSO_4(s) + 4H_2O(l)

Reducing action, acidic medium (here H2O2H_2O_2 is itself oxidised to O2O_2):

2MnO4−+6H++5H2O2→2Mn2++8H2O+5O22MnO_4^- + 6H^+ + 5H_2O_2 \rightarrow 2Mn^{2+} + 8H_2O + 5O_2

HOCl+H2O2→H3O++Cl−+O2HOCl + H_2O_2 \rightarrow H_3O^+ + Cl^- + O_2

Oxidising action, basic medium:

2Fe2++H2O2→2Fe3++2OH−2Fe^{2+} + H_2O_2 \rightarrow 2Fe^{3+} + 2OH^-

Mn2++H2O2→Mn4++2OH−Mn^{2+} + H_2O_2 \rightarrow Mn^{4+} + 2OH^- …

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