Detection reactions using hydrogen peroxide

Complexes with titanyl sulfate and with chromate

With colorless titanyl sulfate, a deep yellow titanium peroxo complex is formed.

TiO2+ + H2O2 -> [TiO2]2+ + H2O

This reaction can also be used to detect dissolved titanium ions.

Cr2O72- + 4 H2O2 -> 2 [CrO5(OH)] + 3 H2O

In the same way, a deep blue colored chromium-peroxo-hydroxo complex is formed from dichromate ions.

In both cases it is not an oxidation, but a complex formation reaction!

Catalyzed decomposition reactions (disproportionation)

If solid manganese dioxide is added, the mixture will foam up vigorously. Oxygen is formed.

2 H2O2 -> 2 H2O + O2

Reduction of potassium permanganate

Compared to strong oxidizing agents, H2O2 acts as a reducing agent. A good example is the reaction of permanganate ions with hydrogen peroxide.

2 MnO4 + 5 H2O2 + 6 H+ -> 2 Mn2+ + 8 H2O + 5 O2

Oxidation of manganese (II) to manganese dioxide

Hydrogen peroxide is, however, better known for its oxidizing effect. In alkaline solutions, it oxidizes manganese (II) to manganese (IV), which precipitates as manganese dioxide (manganese oxide hydroxide).

Mn2+ + H2O2 + 2 OH -> MnO(OH) + 2 H2O

Oxidation of iodide

H2O2 releases elemental iodine from iodide. It is important that the solution must be acidic, otherwise the oxidizing power of H2O2 is not sufficient.

H2O2 + 2 H+ + 2I -> 2 H2O + I2

Oxidation of lead sulfide

Black lead sulfide is oxidized to colorless lead sulfate in a neutral solution.

PbS + 4 H2O2 -> PbSO4 + 4 H2O