Question

Which of the following molecule has zero dipole moment?

• A. \(BF_3\)
• B. \(CH_2Cl_2\)
• C. \(NH_3\)
• D. \(SO_2\)
• E. \(NF_3\)

Hint:

For zero dipole moment, check molecular symmetry. Even if bonds are polar, symmetry can cancel the dipoles completely.

Answer 1

The Correct Option is A

Step 1: Recall the concept of dipole moment.
Dipole moment is a measure of the separation of positive and negative charges in a molecule. It depends on both bond polarity and molecular geometry. For a molecule to have zero dipole moment, the vector sum of all bond dipoles must cancel out.

Step 2: Analyze the geometry of \(BF_3\).
\(BF_3\) has a trigonal planar geometry with bond angles of \(120^\circ\). The three \(B-F\) bonds are identical and symmetrically arranged in a plane.

Step 3: Check dipole cancellation in \(BF_3\).
Each \(B-F\) bond is polar, but due to perfect symmetry, the dipole moments cancel each other out. Therefore, the net dipole moment is zero.

Step 4: Analyze \(CH_2Cl_2\).
This molecule has a tetrahedral shape, but the substituents are not identical (H and Cl). Hence, dipoles do not cancel, and it has a non-zero dipole moment.

Step 5: Analyze \(NH_3\), \(SO_2\), and \(NF_3\).
\(NH_3\) has a trigonal pyramidal shape, \(SO_2\) is bent, and \(NF_3\) is also trigonal pyramidal. All these geometries are asymmetrical, so they have non-zero dipole moments.

Step 6: Identify the only symmetric molecule.
Among the given options, only \(BF_3\) has perfect symmetry leading to complete cancellation of dipole moments.

Step 7: State the final answer.
Thus, the molecule with zero dipole moment is:
\[ \boxed{BF_3} \] which matches option \((1)\).