Acidified permanganate solution does not oxidise:

Options

A. `C_(2)O_(4)^(2-)` (aq.)
B. `NO_(3)^(-)` (aq.)
C. `S^(2-)` (aq.)
D. `F^(-)`(aq.)

Explanation

To determine which species is not oxidized by acidified permanganate solution (KMnO4), we need to analyze the oxidation states of various compounds and their ability to be oxidized. Here’s a step-by-step solution:

### Step 1: Understand the Oxidizing Agent
KMnO4 (potassium permanganate) in an acidic medium acts as a strong oxidizing agent. The manganese in KMnO4 has an oxidation state of +7.

### Step 2: Identify the Compounds
We will consider the following compounds that may or may not be oxidized by KMnO4:
1. Oxalate ion (C2O4^2-)
2. Nitrate ion (NO3^-)
3. Sulfide ion (S^2-)
4. Fluoride ion (F^-)

### Step 3: Analyze Each Compound
- **Oxalate ion (C2O4^2-)**:
- Oxidation state of carbon in oxalate can be calculated as follows:
- Let x be the oxidation state of carbon.
- 2x - 8 = -2 (because there are two oxygens with -2 each)
- Solving gives x = +3.
- Oxalate can be oxidized to CO2, where carbon is in the +4 oxidation state. Thus, it can be oxidized.

- **Nitrate ion (NO3^-)**:
- The oxidation state of nitrogen in nitrate can be calculated:
- Let x be the oxidation state of nitrogen.
- x - 6 = -1 (since there are three oxygens with -2 each)
- Solving gives x = +5.
- Nitrate cannot be oxidized further as it is already at its maximum oxidation state of +5.

- **Sulfide ion (S^2-)**:
- The oxidation state of sulfur in sulfide is -2.
- Sulfide can be oxidized to higher oxidation states (up to +6 in sulfate). Thus, it can be oxidized.

- **Fluoride ion (F^-)**:
- The oxidation state of fluorine in fluoride is -1.
- Fluoride can be oxidized to F2 (where fluorine is in the 0 oxidation state). Thus, it can be oxidized.

### Step 4: Conclusion
Among the compounds analyzed, the nitrate ion (NO3^-) does not get oxidized by acidified permanganate solution because it is already in its maximum oxidation state of +5.

### Final Answer
**Acidified permanganate solution does not oxidize the nitrate ion (NO3^-).**

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