Which of the following is non-polar molecular solid?

Options

A. SiC
B. Naphthlene
C. HCl
D. AIN

Answer

To determine which of the provided options is a non-polar molecular solid, we need to analyze each option based on their molecular structure and polarity.

### Step-by-Step Solution:

1. **Understanding Molecular Solids**:
- Molecular solids are composed of molecules held together by Van der Waals forces. These forces are relatively weak compared to ionic or covalent bonds.

2. **Analyzing Option A: SiC (Silicon Carbide)**:
- Silicon carbide has a structure represented as Si≡C (triple bond).
- This compound is known to be polar due to the difference in electronegativity between silicon and carbon.
- **Conclusion**: SiC is a polar molecule, so it cannot be a non-polar molecular solid.

3. **Analyzing Option B: Naphthalene**:
- Naphthalene consists of two fused benzene rings, which gives it a planar structure.
- The symmetry of the naphthalene molecule results in a dipole moment (μ) equal to zero, indicating that it is non-polar.
- **Conclusion**: Naphthalene is a non-polar molecular solid.

4. **Analyzing Option C: HCl (Hydrochloric Acid)**:
- HCl has a linear structure where hydrogen and chlorine have a significant difference in electronegativity.
- This results in a dipole moment (μ) not equal to zero, making HCl a polar molecule.
- **Conclusion**: HCl is a polar molecule, so it cannot be a non-polar molecular solid.

5. **Analyzing Option D: AlN (Aluminum Nitride)**:
- Aluminum nitride has a structure represented as Al≡N (triple bond).
- Similar to SiC, AlN is also polar due to the difference in electronegativity between aluminum and nitrogen.
- **Conclusion**: AlN is a polar molecule, so it cannot be a non-polar molecular solid.

### Final Answer:
The non-polar molecular solid among the options is **Naphthalene (Option B)**.