Which of the following cannot reduce the acidified solution of permanganate?

Options

A. `(COOH)_2`
B. `H_2`
C. Nascent hydrogen
D. `Fe^(2+)` ions

Explanation

To determine which of the following cannot reduce the acidified solution of permanganate, we will analyze each option provided. The options are:

1. Oxalic acid (COH)
2. Iron(II) ions (Fe²⁺)
3. Nascent hydrogen
4. Hydrogen gas (H₂)

### Step-by-Step Solution:

**Step 1: Analyze Oxalic Acid (COH)**
- Oxalic acid is known to be a good reducing agent and is commonly used for the standardization of permanganate solutions. It can reduce permanganate ions (MnO₄⁻) to manganese(II) ions (Mn²⁺) in acidic medium.
- **Conclusion**: Oxalic acid can reduce permanganate.

**Step 2: Analyze Iron(II) Ions (Fe²⁺)**
- Iron(II) ions are also known to act as reducing agents. In acidic conditions, Fe²⁺ can reduce MnO₄⁻ to Mn²⁺.
- **Conclusion**: Iron(II) ions can reduce permanganate.

**Step 3: Analyze Nascent Hydrogen**
- Nascent hydrogen is highly reactive and can act as a reducing agent. It can reduce permanganate ions in acidic conditions.
- **Conclusion**: Nascent hydrogen can reduce permanganate.

**Step 4: Analyze Hydrogen Gas (H₂)**
- Hydrogen gas (H₂) does not act as a strong reducing agent under acidic conditions. When H₂ is introduced to an acidified permanganate solution, it does not effectively reduce the permanganate ions. Instead, H₂ tends to form hydrides with metals or can react explosively with oxygen.
- **Conclusion**: Hydrogen gas cannot reduce permanganate.

### Final Answer:
The species that cannot reduce the acidified solution of permanganate is **Hydrogen gas (H₂)**.

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