Which of the following oxide cannot act as a reducing agent ?

Options

A. `NO_2`
B. `SO_2`
C. `CO_2`
D. `ClO_2`

Answer

To determine which oxide cannot act as a reducing agent, we need to analyze the oxidation states of the elements in the given oxides and their ability to lose electrons. A reducing agent is a substance that can donate electrons to another substance, thereby reducing it while itself being oxidized.

### Step-by-Step Solution:

1. **Understanding Reducing Agents**:
- A reducing agent is a substance that loses electrons and is oxidized in the process. The ability to act as a reducing agent depends on the oxidation state of the element in the compound and its capacity to lose electrons.

2. **Analyzing the Given Oxides**:
- Let's consider the four oxides mentioned in the question:
- **Option 1**: NO2 (Nitrogen Dioxide)
- **Option 2**: SO2 (Sulfur Dioxide)
- **Option 3**: CO2 (Carbon Dioxide)
- **Option 4**: ClO2 (Chlorine Dioxide)

3. **Determining Oxidation States**:
- **NO2**: The oxidation state of nitrogen in NO2 is +4. Nitrogen can be oxidized to +5, thus it can act as a reducing agent.
- **SO2**: The oxidation state of sulfur in SO2 is +4. Sulfur can be oxidized to +6, so it can also act as a reducing agent.
- **CO2**: The oxidation state of carbon in CO2 is +4. Carbon cannot be oxidized further (it can only go up to +4), so it cannot act as a reducing agent.
- **ClO2**: The oxidation state of chlorine in ClO2 is +4. Chlorine can be oxidized to +5 or +7, thus it can act as a reducing agent.

4. **Conclusion**:
- Among the given oxides, **CO2** cannot act as a reducing agent because carbon is already at its maximum oxidation state of +4 and cannot lose any more electrons.

### Final Answer:
The oxide that cannot act as a reducing agent is **CO2** (Option 3).