Which of the following can acts as a reducing agent ?

Options

A. `H_(2)S`
B. `HNO_(3)`
C. `FeSO_(4)`
D. `SnCl_(2)`

Answer

To determine which of the given substances can act as a reducing agent, we need to analyze the oxidation states of the elements in each compound. A reducing agent is a substance that can donate electrons to another substance, thereby reducing it. This typically corresponds to the substance having a lower oxidation state.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are H2S, HNO3, FeSO4, and SnCl2.

2. **Calculate the Oxidation State of Sulfur in H2S**:
- The formula for H2S is: H2 + S = 0.
- Hydrogen (H) has an oxidation state of +1. Therefore, for 2 hydrogen atoms: 2(+1) + X = 0.
- This gives us: 2 + X = 0 → X = -2.
- **Oxidation State of S in H2S = -2**.

3. **Calculate the Oxidation State of Nitrogen in HNO3**:
- The formula for HNO3 is: H + N + 3O = 0.
- Hydrogen (H) is +1, and Oxygen (O) is -2. Thus: +1 + X + 3(-2) = 0.
- This gives us: +1 + X - 6 = 0 → X - 5 = 0 → X = +5.
- **Oxidation State of N in HNO3 = +5**.

4. **Calculate the Oxidation State of Iron in FeSO4**:
- The formula for FeSO4 is: Fe + SO4 = 0.
- The sulfate ion (SO4) has a charge of -2. Thus: X + (-2) = 0.
- This gives us: X - 8 = -2 → X = +6.
- **Oxidation State of Fe in FeSO4 = +6**.

5. **Calculate the Oxidation State of Tin in SnCl2**:
- The formula for SnCl2 is: Sn + 2Cl = 0.
- Chlorine (Cl) has an oxidation state of -1. Thus: X + 2(-1) = 0.
- This gives us: X - 2 = 0 → X = +2.
- **Oxidation State of Sn in SnCl2 = +2**.

6. **Compare the Oxidation States**:
- H2S: S = -2 (lowest oxidation state)
- HNO3: N = +5 (highest oxidation state)
- FeSO4: Fe = +6 (highest oxidation state)
- SnCl2: Sn = +2 (higher oxidation state)

7. **Identify the Reducing Agent**:
- The substance with the lowest oxidation state is H2S (S = -2).
- Since H2S can donate electrons (due to the low oxidation state of sulfur), it acts as a reducing agent.

### Conclusion:
The correct answer is **H2S**, which acts as a reducing agent.