Question

H2o2 acting as an oxidizing agent in acidic solution why

Answer 1

My chemistry books details out both, the oxidizing and reducing properties of hydrogen peroxide, H2O2HX2OX2.

Its reducing properties:

It reduces ClCl to HClHCl

It reduces Ag2OAgX2O to AgAg

It reduces K3[Fe(CN)6]KX3[Fe(CN)X6] (potassium ferricyanide) to K4[Fe(CN)6]KX4[Fe(CN)X6](potassium ferrocyanide)

Etc.

Half equations for reduction:

In acidic medium: H2O2⟶2H++O2+2e−HX2OX2⟶2HX++OX2+2eX−

In basic medium: H2O2+2OH−⟶2H2O+O2+2e−HX2OX2+2OHX−⟶2HX2O+OX2+2eX−

Its oxidizing properties:

It oxidizes sulphites to sulphates

It oxidizes arsenites to arsenates

It oxidizes nitrites to nitrates

It oxidizes potassium ferricyanide to potassium ferrocyanide

Etc.

Half equations for oxidation:

In acidic medium: H2O2+2H++2e−⟶2H2OHX2OX2+2HX++2eX−⟶2HX2O

In basic medium: H2O2+2e−⟶2OH−HX2OX2+2eX−⟶2OHX−

I was unable to find any pattern in all of the reactions I studied above (except for potassium ferrocyanide, for which the medium triggers the electron addition/removal) to recognize when hydrogen peroxide behaves as an oxidising agent and when it behaves as a reducing agent.