Question

The reaction in which hydrogen peroxide act as a reducing agent is:
A. $PbS + 4{H_2}{O_2} \to PbS{O_4} + 4{H_2}O$
B. $2KI + {H_2}{O_2} \to 2KOH + {I_2}$
C. $2FeS{O_4} + {H_2}S{O_4} + {H_2}{O_2} \to Fe{(S{O_4})_3} + 2{H_2}O$
D. ${H_2}S{O_3} + {H_2}{O_2} \to {H_2}S{O_4} + {H_2}O$
E. $A{g_2}O + {H_2}{O_2} \to 2Ag + {H_2}O + {O_2}$

Answer 1

Hint: Hydrogen peroxide behaves as oxidizing as well as reducing agents in both acidic as well as alkaline solutions. The oxidation state of oxygen in hydrogen peroxide is -1 can be oxidized to ${O_2}$ (in zero oxidation state) and reduced to ${H_2}O$ (in -2 oxidation state).

Complete step by step answer:
If we talk about option A, the given reaction involves the formation of lead sulphate and water by oxidation of lead sulphide by hydrogen peroxide. In this reaction hydrogen peroxide reduces to ${H_2}O$ hence, it acts as an oxidizing agent.
If we talk about option B, the reaction involves the formation of iodine from potassium iodide, in this reaction the oxidation state of iodine changes from -1 to zero hence it gets oxidized thus we can say here also hydrogen peroxide act as an oxidizing agent.
If we talk about option C, this reaction involves the formation of ferric sulphate from ferrous sulphate. Here the oxidation state of iron changes from +2 to +3. Hence, also hydrogen peroxide acts as an oxidising agent.
If we talk about option D, in this reaction oxidation state of sulphur changes from +4 to +6, there is also an increase in oxidation state hence again hydrogen peroxide acts as an oxidising agent.
And if we talk about the option E, in this reaction silver oxide is reduced to silver in the presence of hydrogen peroxide hence it acts as a reducing agent.

So, the correct answer is Option E.

Note: Since the hydrogen peroxide is a weak reducing agent it only acts as a reducing agent in the presence of a strong oxidising agent in acidic as well as in basic medium. There is the formation of molecular oxygen when hydrogen peroxide reacts with a strong oxidising agent.