Question

Identify a pair of molecules having zero dipole moment.

• A. \(\text{BF}_{3}\) and \(\text{HBr}\)
• B. \(\text{CH}_{4}\) and \(\text{NF}_{3}\)
• C. \(\text{NH}_{3}\) and \(\text{H}_{2}\text{O}\)
• D. \(\text{CCl}_{4}\) and \(\text{CO}_{2}\)

Hint:

Zero dipole moment needs bond dipoles that cancel because of a symmetrical molecular shape.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
A molecule has zero dipole moment when its bond dipoles cancel due to a symmetrical shape.

Step 2: Check the pair CCl4 and CO2
\(\text{CCl}_{4}\) is a regular tetrahedron, and \(\text{CO}_{2}\) is linear (O=C=O). In both, the bond dipoles cancel.

Step 3: Check the other pairs
\(\text{HBr}\) is a polar diatomic molecule. \(\text{NF}_{3}\) and \(\text{NH}_{3}\) are pyramidal and \(\text{H}_{2}\text{O}\) is bent, so they are polar. Only \(\text{BF}_{3}\) and \(\text{CH}_{4}\) are non-polar among those.

Final Answer:
Carbon tetrachloride and carbon dioxide both have zero dipole moment. \[ \boxed{\text{(D) }\text{CCl}_{4}\text{ and CO}_{2}} \]