Assertion:- `K_(3)[Fe(CN)_(6)]` is an example of low spin complex.
Reason:- This complex is paramagnetic in nature.

Options

A. If both Assertion `&` Reason are True `&` the Reason is a correct explanation of the Assertion.
B. If both Assertion `&` Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion `&` Reason are False.

Answer

To solve the assertion and reason question regarding the complex \( K_3[Fe(CN)_6] \), we will analyze both statements step by step.

### Step 1: Analyze the Assertion
**Assertion:** \( K_3[Fe(CN)_6] \) is an example of a low spin complex.

1. **Identify the Ligand:** The ligand in this complex is \( CN^- \) (cyanide), which is known to be a strong field ligand according to the spectrochemical series.
2. **Understand Low Spin Complexes:** Low spin complexes are formed when strong field ligands cause the pairing of electrons in the d-orbitals before they occupy higher energy orbitals. This leads to fewer unpaired electrons.
3. **Determine the Oxidation State of Iron:** In \( K_3[Fe(CN)_6] \), the \( Fe \) is in the +3 oxidation state (since \( CN^- \) has a -1 charge and there are six of them, the total negative charge is -6, thus \( Fe \) must be +3).
4. **Electron Configuration of \( Fe^{3+} \):** The electron configuration of neutral iron (Fe) is \( [Ar] 3d^6 4s^2 \). For \( Fe^{3+} \), we remove two electrons from the 4s orbital and one from the 3d orbital, resulting in \( 3d^5 \).
5. **Conclusion on Assertion:** Since \( CN^- \) is a strong field ligand, it will lead to the pairing of electrons in the \( 3d \) orbitals, confirming that \( K_3[Fe(CN)_6] \) is indeed a low spin complex.

### Step 2: Analyze the Reason
**Reason:** This complex is paramagnetic in nature.

1. **Definition of Paramagnetism:** A complex is paramagnetic if it has unpaired electrons.
2. **Count Unpaired Electrons:** In the case of \( K_3[Fe(CN)_6] \), after considering the strong field nature of \( CN^- \), the \( 3d^5 \) configuration will have all five electrons paired due to the strong field effect.
3. **Conclusion on Reason:** Since all the electrons are paired, \( K_3[Fe(CN)_6] \) is not paramagnetic but rather diamagnetic.

### Final Conclusion
- **Assertion:** True (it is a low spin complex).
- **Reason:** False (it is not paramagnetic; it is diamagnetic).

### Answer
Both the assertion and reason are true, but the reason is not the correct explanation for the assertion.