Question

Identify the type of intermolecular force present between benzene and ammonia.

• A. Hydrogen bonding
• B. Dipole-induced dipole interaction
• C. Dipole-dipole interaction
• D. Ion-dipole interaction

Hint:

A quick rule to remember:
• Polar + Polar \(\rightarrow\) Dipole-dipole interaction
• Non-polar + Non-polar \(\rightarrow\) London dispersion force
• Polar + Non-polar \(\rightarrow\) Dipole-induced dipole interaction
• Ion + Polar molecule \(\rightarrow\) Ion-dipole interaction

Answer 1

The Correct Option is B

Concept: Intermolecular forces depend on the polarity of the interacting molecules.
• Polar molecules possess a permanent dipole moment.
• Non-polar molecules do not possess a permanent dipole moment.
• A polar molecule can induce temporary polarity in a nearby non-polar molecule, producing dipole-induced dipole attraction.

Step 1: Identifying the nature of benzene.
Benzene (\(\mathrm{C_6H_6}\)) is a highly symmetrical planar molecule. Although each C-H bond has a small polarity, the overall dipole moments cancel due to symmetry. Therefore: \[ \mu = 0 \] Hence, benzene is a non-polar molecule.

Step 2: Identifying the nature of ammonia.
Ammonia (\(\mathrm{NH_3}\)) has a trigonal pyramidal geometry because nitrogen contains one lone pair. The bond dipoles do not cancel. Therefore ammonia possesses a permanent dipole moment. Hence, ammonia is a polar molecule.

Step 3: Determining the intermolecular interaction.
When a polar molecule approaches a non-polar molecule:
• The permanent dipole of the polar molecule distorts the electron cloud of the non-polar molecule.
• This creates an induced dipole in the non-polar molecule.
• Attraction develops between the permanent dipole and the induced dipole. Thus, between benzene and ammonia, the intermolecular force is: \[ \boxed{\text{Dipole-induced dipole interaction}} \] Therefore, the correct answer is: \[ \boxed{(B)\ \text{Dipole-induced dipole interaction}} \]