Which among the following will not act as a reducing agent?

Options

A. `KNO_2`
B. KI
C. `NaNO_3`
D. `H_2S`

Answer

To determine which among the given compounds will not act as a reducing agent, we need to analyze each compound based on its ability to undergo oxidation. A reducing agent is a substance that donates electrons to another substance, thereby reducing it, while itself getting oxidized.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- Potassium nitrite (KNO2)
- Potassium iodide (KI)
- Sodium nitrate (NaNO3)
- Hydrogen sulfide (H2S)

2. **Examine Potassium Nitrite (KNO2)**:
- The oxidation state of nitrogen in KNO2 is +3.
- It can be oxidized to +5 (as in NO3-).
- Since it can donate electrons, KNO2 can act as a reducing agent.

3. **Examine Potassium Iodide (KI)**:
- The oxidation state of iodine in KI is -1.
- It can be oxidized to 0 (as in I2).
- KI can also act as a reducing agent because it can donate electrons.

4. **Examine Sodium Nitrate (NaNO3)**:
- The oxidation state of nitrogen in NaNO3 is +5.
- This is the maximum oxidation state for nitrogen.
- Since it cannot be oxidized further (it cannot donate electrons), NaNO3 will not act as a reducing agent.

5. **Examine Hydrogen Sulfide (H2S)**:
- The oxidation state of sulfur in H2S is -2.
- It can be oxidized to +4 (as in SO3) or +6 (as in SO4).
- Therefore, H2S can act as a reducing agent because it can donate electrons.

6. **Conclusion**: Among the given compounds, sodium nitrate (NaNO3) is the only one that cannot act as a reducing agent because it cannot be oxidized further.

### Final Answer:
**Sodium nitrate (NaNO3) will not act as a reducing agent.**

---