In which of the following reactions, hydrogen peroxide acts as an oxidizing agent ?

Options

A. `HOCI + H_(2)O_(2) to H_(3)O^(+) + CI^(-) + O_(2)`
B. `I_(2) + H_(2)O_(2) + 2OH^(-) to 2I^(-) + 2H_(2)O + O_(2)`
C. `PbS + 4H_(2)O_(2) to PbSO_(4) + 4H_(2)O`
D. `2MnO_(4)^(-) + 3H_(2)O_(2) to 2MnO_(2) + 3O_(2) + 2H_(2)O + 2OH^(-)`

Answer

To determine in which of the following reactions hydrogen peroxide (H2O2) acts as an oxidizing agent, we need to analyze each option based on the oxidation states of the elements involved in the reactions. An oxidizing agent is a substance that gains electrons (is reduced) while causing another substance to be oxidized (lose electrons).

### Step-by-Step Solution:

1. **Understand the Role of Oxidizing Agents**:
- An oxidizing agent is a substance that oxidizes another substance by accepting electrons. In the process, the oxidizing agent itself gets reduced.

2. **Analyze Each Reaction**:
- We will go through each option provided in the question and determine the role of H2O2.

3. **Option A: HOCl + H2O2 → H3O+ + Cl- + O2**:
- In this reaction, the oxidation state of chlorine changes from +1 in HOCl to -1 in Cl-. This indicates that chlorine is being reduced, meaning H2O2 is acting as a reducing agent, not an oxidizing agent.
- **Conclusion**: H2O2 does not act as an oxidizing agent in this reaction.

4. **Option B: I2 + H2O2 + 2OH- → 2I- + 2H2O + O2**:
- Here, the oxidation state of iodine changes from 0 in I2 to -1 in I-. This indicates that iodine is being reduced, which means H2O2 is again acting as a reducing agent.
- **Conclusion**: H2O2 does not act as an oxidizing agent in this reaction.

5. **Option C: PbS + H2O2 → PbSO4 + 4H2O**:
- In this reaction, the oxidation state of sulfur changes from -2 in PbS to +6 in PbSO4. This indicates that sulfur is being oxidized, which means H2O2 is acting as an oxidizing agent.
- **Conclusion**: H2O2 acts as an oxidizing agent in this reaction.

6. **Option D: MnO4- + H2O2 → MnO2 + O2 + H2O + 2OH-**:
- In this reaction, the oxidation state of manganese changes from +7 in MnO4- to +4 in MnO2. This indicates that manganese is being reduced, which means H2O2 is acting as a reducing agent.
- **Conclusion**: H2O2 does not act as an oxidizing agent in this reaction.

7. **Final Conclusion**:
- The only reaction in which H2O2 acts as an oxidizing agent is **Option C: PbS + H2O2 → PbSO4 + 4H2O**.

### Summary of Findings:
- **Option A**: H2O2 is a reducing agent.
- **Option B**: H2O2 is a reducing agent.
- **Option C**: H2O2 is an oxidizing agent (correct answer).
- **Option D**: H2O2 is a reducing agent.