In the following questions, a statement of assertion (A) is followed by a statement of reason (R )
A : All P-Cl bond lengths are equal in `PCl_(3)` but different in `PCl_(5)`
R : Hybrid state of central atom is different in both molecules.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements , then mark (4).

Answer

To solve the question regarding the assertion and reason about the bond lengths in PCl3 and PCl5, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
**Assertion (A)**: All P-Cl bond lengths are equal in PCl3 but different in PCl5.

- **PCl3 Structure**: Phosphorus trichloride (PCl3) has a trigonal pyramidal shape due to the presence of one lone pair on phosphorus. The three P-Cl bonds are formed from sp³ hybridized orbitals. Since the geometry is symmetrical, all P-Cl bond lengths are equal.

- **PCl5 Structure**: Phosphorus pentachloride (PCl5) has a trigonal bipyramidal structure. It has five P-Cl bonds, but due to the different positions (axial and equatorial) of these bonds, the bond lengths vary. The equatorial bonds are shorter and equivalent, while the axial bonds are longer due to increased electron repulsion.

### Conclusion for Assertion
The assertion is **true** because all P-Cl bond lengths are indeed equal in PCl3 and different in PCl5.

### Step 2: Analyze the Reason
**Reason (R)**: Hybrid state of the central atom is different in both molecules.

- **Hybridization of PCl3**: The hybridization of phosphorus in PCl3 is sp³, which accounts for the three equivalent P-Cl bonds.

- **Hybridization of PCl5**: The hybridization of phosphorus in PCl5 is sp³d, which leads to the formation of five bonds with different lengths due to their positions (axial vs. equatorial).

### Conclusion for Reason
The reason is also **true** because the hybridization states of phosphorus in PCl3 and PCl5 are indeed different.

### Step 3: Evaluate the Relationship Between Assertion and Reason
While both the assertion and reason are true, the reason does not provide a direct explanation for the assertion. The equality of bond lengths in PCl3 and the inequality in PCl5 is a consequence of their geometrical arrangements rather than solely due to the difference in hybridization.

### Final Conclusion
The correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion. Therefore, the answer is option 2.

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