In the reaction of hydrogen peroxide with iron (II) ion in acidic solution to form iron (III) ion and water,
the oxidizing agent is
I assume you posted the earlier question about the H2O2 and ferrous to ferric reaction. If not, look a couple of posts below and you will see my response. The oxidizing agent is the one which is reduced. Reduction is the gain of electrons.
To determine the oxidizing agent in a chemical reaction, we need to examine the changes in oxidation states of the elements involved.
In the given reaction:
H₂O₂ + Fe²⁺ → Fe³⁺ + H₂O
Iron (II) ion (Fe²⁺) is being oxidized to Iron (III) ion (Fe³⁺), which means it is losing electrons and undergoing an increase in oxidation state.
Hydrogen peroxide (H₂O₂) does not change its oxidation state during the reaction, remaining as -1.
Therefore, in this reaction, hydrogen peroxide is acting as the reducing agent, while iron (II) ion is acting as the oxidizing agent.