Question

Which of the following molecules does not exhibit dipole moment?
(i) CCl$_4$
(ii) CO$_2$
(iii) NH$_3$
(iv) CHCl$_3$
(v) H$_2$O
(vi) CH$_3$–O–CH$_3$

• A. (ii), (v), (iv)
• B. (i), (iii), (vi)
• C. (i), (ii)
• D. (iii), (iv), (vi)

Hint:

Symmetry is key! Linear or tetrahedral molecules with identical substituents cancel dipoles.

Answer 1

The Correct Option is C

Step 1: Understand dipole moment.
Dipole moment arises from the vector sum of all bond dipoles. A molecule may have polar bonds but net dipole moment zero if it’s symmetric. Step 2: Analyze each molecule.
(i) CCl$_4$: Tetrahedral, symmetrical — net dipole moment = 0
(ii) CO$_2$: Linear, symmetrical — dipoles cancel — net = 0
(iii) NH$_3$: Trigonal pyramidal, lone pair — dipole present
(iv) CHCl$_3$: Asymmetric — dipole moment present
(v) H$_2$O: Angular shape — strong dipole due to lone pairs
(vi) CH$_3$–O–CH$_3$: Bent structure — dipole moment exists Hence, only (i) and (ii) have no net dipole moment.