Which one of the following compounds does not decolourise an acidified aqueous solution of `KMnO_(4)`

Options

A. `FeCl_(3)`
B. `FeSO_(4)`
C. `SO_(2)`
D. `H_(2)O_(2)`

Answer

To solve the problem of identifying which compound does not decolorize an acidified aqueous solution of KMnO4 (potassium permanganate), we will analyze each of the given compounds based on their oxidation states and their ability to act as reducing agents.

### Step-by-Step Solution:

1. **Understand the Nature of KMnO4**:
- Potassium permanganate (KMnO4) is a strong oxidizing agent. In acidic solution, it appears purple due to the MnO4^- ion, where manganese is in the +7 oxidation state.

2. **Identify the Compounds**:
- The compounds to be analyzed are:
- Ferric chloride (FeCl3)
- Ferrous sulfate (FeSO4)
- Sulfur dioxide (SO2)
- Hydrogen peroxide (H2O2)

3. **Analyze Ferric Chloride (FeCl3)**:
- In FeCl3, iron is in the +3 oxidation state. Since it is already in a high oxidation state, it cannot reduce KMnO4 (which would require it to be reduced itself). Therefore, FeCl3 does not decolorize KMnO4.

4. **Analyze Ferrous Sulfate (FeSO4)**:
- In FeSO4, iron is in the +2 oxidation state. It can act as a reducing agent and can reduce KMnO4, thus decolorizing it.

5. **Analyze Sulfur Dioxide (SO2)**:
- Sulfur dioxide can act as a reducing agent. It can reduce KMnO4 from +7 to lower oxidation states, thus decolorizing it.

6. **Analyze Hydrogen Peroxide (H2O2)**:
- Hydrogen peroxide can also act as a reducing agent. It can reduce KMnO4, leading to decolorization.

7. **Conclusion**:
- Among the compounds analyzed, only ferric chloride (FeCl3) does not decolorize an acidified aqueous solution of KMnO4.

### Final Answer:
**Ferric chloride (FeCl3) does not decolorize an acidified aqueous solution of KMnO4.**