What type of intermolecular forces exist between `NH_3 and C_6H_6` ?

Options

A. Dispersion forces
B. Dipole - dipole forces
C. Dipole - induced dipole forces and dispersion forces
D. Dispersion and dipole - dipole forces

Answer

To determine the type of intermolecular forces that exist between ammonia (NH₃) and benzene (C₆H₆), we need to analyze the properties of each molecule and how they interact with each other.

### Step-by-Step Solution:

1. **Identify the Nature of NH₃:**
- Ammonia (NH₃) is a polar molecule. This is due to the presence of a nitrogen atom that has a lone pair of electrons, creating a dipole moment. The nitrogen atom is more electronegative than hydrogen, causing the nitrogen end to be partially negative (δ-) and the hydrogen ends to be partially positive (δ+).

**Hint:** Remember that polar molecules have a permanent dipole moment due to differences in electronegativity between atoms.

2. **Identify the Nature of C₆H₆:**
- Benzene (C₆H₆) is a non-polar molecule. Although it has a symmetrical structure with alternating double bonds, the electron distribution is uniform, leading to no overall dipole moment.

**Hint:** Non-polar molecules do not have a significant difference in electronegativity between their constituent atoms, resulting in no permanent dipole.

3. **Determine the Intermolecular Forces:**
- Between a polar molecule (NH₃) and a non-polar molecule (C₆H₆), the primary interaction will be a dipole-induced dipole interaction. The polar NH₃ can induce a dipole in the non-polar C₆H₆ by distorting its electron cloud due to the presence of the NH₃ dipole.

**Hint:** Dipole-induced dipole forces occur when a polar molecule induces a temporary dipole in a non-polar molecule.

4. **Consider Dispersion Forces:**
- Both NH₃ and C₆H₆ will also experience London dispersion forces (or van der Waals forces), which are present in all molecules, regardless of polarity. These forces arise from temporary fluctuations in electron density that create instantaneous dipoles.

**Hint:** Dispersion forces are always present, but they are generally weaker than dipole-dipole interactions.

5. **Conclusion:**
- The intermolecular forces that exist between NH₃ and C₆H₆ are:
- Dipole-induced dipole forces (due to the polar nature of NH₃ inducing a dipole in C₆H₆).
- London dispersion forces (present in both molecules).

**Final Answer:** The intermolecular forces between NH₃ and C₆H₆ are dipole-induced dipole forces and dispersion forces.