Which is true statement about `KMnO_4`?

Options

A. Its solution is unstable in acidic medium.
B. It has purple colour.
C. `MnO_4^(ɵ)` changes to `Mn^(2+)` in basic solution.
D. It is self indicator in `Fe&(2+)` or `C_2O_4^(2-)` titration.

Answer

To determine which statements about KMnO₄ (potassium permanganate) are true, we will analyze each option provided in the question step by step.

### Step 1: Analyze Option 1
**Statement:** Its solution is unstable in acidic medium.

**Explanation:** KMnO₄ is known to be stable in neutral and basic solutions but can decompose in acidic solutions. In acidic medium, it can undergo reduction, which can lead to the formation of Mn²⁺ ions. Therefore, this statement is **true**.

### Step 2: Analyze Option 2
**Statement:** It has a purple color.

**Explanation:** KMnO₄ is well-known for its deep purple color, which is due to the presence of the MnO₄⁻ ion. The color arises from the electronic transitions of the manganese ion. Therefore, this statement is also **true**.

### Step 3: Analyze Option 3
**Statement:** MnO₄⁻ changes to Mn²⁺ in basic solution.

**Explanation:** In basic solutions, KMnO₄ does not reduce to Mn²⁺; instead, it typically reduces to MnO₂ (manganese dioxide). The reduction of MnO₄⁻ to Mn²⁺ primarily occurs in acidic conditions. Therefore, this statement is **false**.

### Step 4: Analyze Option 4
**Statement:** It is a self-indicator in Fe²⁺ or C₂O₄²⁻ titration.

**Explanation:** KMnO₄ is often used as a self-indicator in redox titrations involving Fe²⁺ ions or oxalate ions (C₂O₄²⁻). The solution changes color from purple to colorless as the KMnO₄ is reduced. Therefore, this statement is **true**.

### Conclusion
Based on the analysis of the statements:
- Option 1: True
- Option 2: True
- Option 3: False
- Option 4: True

Thus, the true statements about KMnO₄ are options 1, 2, and 4.