Question

Identify the molecule having a non-zero dipole moment.

• A. $\text{BF}_3$
• B. $\text{CCl}_4$
• C. $\text{CHCl}_3$
• D. $\text{CH}_4$

Hint:

Any compound possessing a perfectly symmetrical basic geometric shape ($\text{AX}_2$ linear, $\text{AX}_3$ trigonal planar, $\text{AX}_4$ tetrahedral) will always have a dipole moment of zero if and only if all surrounding $X$ atoms are completely identical. If you change even one single atom (like switching $\text{CCl}_4$ to $\text{CHCl}_3$), the symmetry shatters and the molecule becomes polar!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the polar molecule with a net permanent dipole moment among the four given covalent compounds.

Step 2: Key Formula or Approach:
A molecule is polar if its bond dipole vectors do not cancel out due to asymmetry in geometry or the presence of different peripheral atoms.

Step 3: Detailed Explanation:
BF₃ (trigonal planar), CH₄ (tetrahedral), and CCl₄ (tetrahedral) are all perfectly symmetric with identical outer atoms, so their dipoles cancel. CHCl₃ has three C–Cl bonds and one C–H bond, breaking the tetrahedral symmetry and resulting in a net downward dipole moment.

Step 4: Final Answer:
The polar molecule is CHCl₃, corresponding to option (C).