Assertion Boiling point of `SiH_(4) gt CH_(4)` whereas boiling point of `SiCI_(4) lt CCI_(4)`
Reasoning Chlorine possesses vacant d-orbitals but hydrogen does not .

Options

A. If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`
B. If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`
C. If `(A)` is correct but `(R )` is incorrect
D. If `(A)` is incorrect but `(R )` is correct

Explanation

To solve the question regarding the assertion and reasoning about the boiling points of SiH₄ and CH₄, as well as SiCl₄ and CCl₄, we will break it down step by step.

### Step 1: Analyze the Assertion
The assertion states that the boiling point of SiH₄ is greater than that of CH₄, while the boiling point of SiCl₄ is less than that of CCl₄.

- **SiH₄ (Silane)** and **CH₄ (Methane)** are both molecular compounds. They are non-polar molecules because they have symmetrical shapes and similar electronegativities between the central atom and hydrogen.
- The boiling point of a substance is influenced by the intermolecular forces present. For non-polar molecules like SiH₄ and CH₄, the primary intermolecular forces are London dispersion forces (Van der Waals forces).

### Step 2: Compare the Molecular Weights
- **Molecular weight of SiH₄**: Silicon (Si) has a molar mass of approximately 28.09 g/mol, and hydrogen (H) has a molar mass of approximately 1.01 g/mol. Therefore, the molar mass of SiH₄ is about 32.15 g/mol.
- **Molecular weight of CH₄**: Carbon (C) has a molar mass of approximately 12.01 g/mol, and thus the molar mass of CH₄ is about 16.04 g/mol.

Since SiH₄ has a higher molecular weight than CH₄, it will have stronger London dispersion forces, leading to a higher boiling point.

### Step 3: Analyze the Boiling Points of SiCl₄ and CCl₄
- **SiCl₄ (Silicon Tetrachloride)** and **CCl₄ (Carbon Tetrachloride)** are also molecular compounds, but they have polar bonds due to the difference in electronegativity between silicon and chlorine, and carbon and chlorine.
- The boiling point of these compounds is influenced by dipole-dipole interactions in addition to London dispersion forces.

### Step 4: Compare the Electronegativity
- Carbon is more electronegative than silicon. Therefore, the dipole-dipole interactions in CCl₄ are stronger than those in SiCl₄. This results in CCl₄ having a higher boiling point than SiCl₄.

### Step 5: Evaluate the Reasoning
The reasoning states that "Chlorine possesses vacant d-orbitals but hydrogen does not." While this statement is true, it does not adequately explain the boiling point differences discussed in the assertion. The boiling point differences are primarily due to molecular weight and the nature of intermolecular forces (London dispersion forces and dipole-dipole interactions).

### Conclusion
- The assertion is correct: SiH₄ has a higher boiling point than CH₄, and SiCl₄ has a lower boiling point than CCl₄.
- The reasoning is also correct, but it does not satisfactorily explain the assertion.

Thus, the answer is: **B. Both are correct statements, but the reason does not explain the assertion satisfactorily.**