Question

Identify incorrectly matched set from the following

• A. Molecules with incomplete octet - BeH2, BC13
• B. Polar molecules - BF3, CCl4
• C. Molecules with expanded octet - PCl5, SF6
• D. Odd electron molecules - NO, NO2

Hint:

When determining the polarity of a molecule, always consider its geometry and electron distribution.

Answer 1

The Correct Option is B

- Molecules with incomplete octet: BeH2 and BC13 have incomplete octets, so this pair is correct.
- Polar molecules: BF3 is a non-polar molecule due to its symmetrical triangular shape, while CCl4 is also non-polar. Hence, the pair is incorrect.
- Molecules with expanded octet: PCl5 and SF6 both have expanded octets, so this pair is correct.
- Odd electron molecules: NO and NO2 are odd electron molecules, so this pair is correct.
Thus, the incorrectly matched pair is \( \boxed{\text{BF3, CCl4}} \).

Answer 2

Step 1: Understand polarity in molecules.
A molecule is polar if it has a net dipole moment due to unequal distribution of electron density.
Nonpolar molecules have symmetrical structures causing the dipole moments to cancel out.

Step 2: Analyze the given molecules.
- \(\text{BF}_3\) (boron trifluoride) has a trigonal planar structure with three identical B–F bonds symmetrically arranged.
The dipole moments cancel out, making \(\text{BF}_3\) nonpolar.

- \(\text{CCl}_4\) (carbon tetrachloride) has a tetrahedral geometry with four identical C–Cl bonds symmetrically arranged.
The dipole moments also cancel out, making \(\text{CCl}_4\) nonpolar.

Step 3: Conclusion.
The set "Polar molecules – BF3, CCl4" is incorrectly matched because both \(\text{BF}_3\) and \(\text{CCl}_4\) are nonpolar molecules.
Hence, this is the incorrect matching.