In which of the following reactions H2O2 acts as a reducing agent?
(a) H2O2 + 2H+ + 2e– → 2H2O
(b) H2O2 – 2e– → O2 + 2H+
(c) H2O2 + 2e– → 2OH–
(d) H2O2 + 2OH– – 2e– → O2 + 2H2O
H2O2 – 2e– → O2 + 2H+
H2O2 + 2OH– – 2e– → O2 + 2H2O
Hydrogen peroxide (H2O2) can act as both an oxidizing agent and a reducing agent because the oxygen atom in H2O2 has an oxidation state of -1, which can either decrease to -2 (reduction, oxidizing agent) or increase to 0 (oxidation, reducing agent). A reducing agent loses electrons and gets oxidized.
Let's analyze each reaction:
Option (a): H2O2 + 2H+ + 2e- → 2H2O
Here, H2O2 gains electrons (reduction), so it acts as an oxidizing agent, not a reducing agent.
Option (b): H2O2 - 2e- → O2 + 2H+
H2O2 loses electrons (oxidation), so it acts as a reducing agent. The oxidation state of oxygen increases from -1 in H2O2 to 0 in O2.
Option (c): H2O2 + 2e- → 2OH-
H2O2 gains electrons (reduction), so it acts as an oxidizing agent. The oxidation state of oxygen decreases from -1 to -2.
Option (d): H2O2 + 2OH- - 2e- → O2 + 2H2O
H2O2 loses electrons (oxidation), so it acts as a reducing agent. The oxidation state of oxygen increases from -1 to 0.
Thus, the reactions where H2O2 acts as a reducing agent are (b) and (d).
Final Answer: (b), (d)
Redox Reactions: Reactions involving transfer of electrons between species. An oxidizing agent gains electrons and gets reduced, while a reducing agent loses electrons and gets oxidized.
Hydrogen Peroxide: A compound that can exhibit both oxidizing and reducing behavior due to the intermediate oxidation state of oxygen (-1).
Change in oxidation state indicates redox behavior:
If oxidation state increases → Oxidation (reducing agent)
If oxidation state decreases → Reduction (oxidizing agent)