`KMnO_4` is prepared from the mineral pyrolusite, `MnO_2` (deep purple colour). It acts as an oxidising agent in the neutral, alkaline as well as acidic medium in acidic medium it is used in volumetric analysis for estimation of `Fe^(2+)`, `Cr_2O_4^(2-)` salts etc. The titrations are carried out in presence of `H_2SO_4`. However, before using it as a titrant, it is first standardised with standard oxalic acid solution or Mohr's salt solution . In one of the experiments on titration 26.8g of dry pure sodium oxalate `(Mw=123gmol^-1)` was dissolved in 1L of distilled water and then 100 mL of `2MH_2SO_4` were added. The solution was cooled. Now to this solution `0.1MKMnO_4` solution was added till a very faint pink colour persisted.
Q. The purple colour of `KMnO_4` is due to

Options

A. incomplete d-subshell
B. ionic nature of `KMnO_4`
C. Charge transfer
D. Resonance in `MnO_4^(ɵ)`ion

Explanation

To answer the question regarding the purple color of KMnO4, we can break down the explanation into clear steps:

### Step-by-Step Solution

1. **Understanding KMnO4**:
- KMnO4, or potassium permanganate, is a compound where manganese (Mn) is in the +7 oxidation state.

2. **Oxidation State of Manganese**:
- In KMnO4, manganese has an oxidation state of +7. This means it has lost 7 electrons compared to its neutral state.

3. **Electronic Configuration**:
- The electronic configuration of manganese in its elemental form (Mn) is [Ar] 4s² 3d⁵. In the +7 oxidation state, all 7 electrons (2 from 4s and 5 from 3d) are removed, resulting in a configuration of [Ar] (which means there are no d or s electrons left).

4. **Color Origin**:
- Despite the absence of d or s electrons, KMnO4 exhibits a purple color. This is due to a phenomenon known as charge transfer.

5. **Charge Transfer Mechanism**:
- In KMnO4, the oxygen atoms act as ligands and can donate electrons to the manganese ion. When the oxygen donates an electron, it changes from O²⁻ to O⁻, effectively allowing manganese to transition from Mn(VII) to Mn(VI) temporarily.

6. **Presence of d Electrons**:
- In the Mn(VI) state, manganese has one d electron. The presence of this d electron allows for electronic transitions that absorb certain wavelengths of light, leading to the observed purple color.

7. **Conclusion**:
- Therefore, the purple color of KMnO4 is primarily due to charge transfer from the ligands (oxygen) to the manganese ion, allowing for electronic transitions that result in color.

### Final Answer:
The purple color of KMnO4 is due to charge transfer from the ligands (oxygen) to the manganese ion, which allows for electronic transitions.

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