`NH_(3)` has a much higher boiling point than `PH_(3)`  because

Options

A. `NH_(3)` has a larger molecular weight
B. `NH_(3)` undergoes umbrella inversion
C. `NH_(3)` forms hydrogen bond
D. `NH_(3)` contains ionic bonds whereas `PH_(3)` contains covalent bonds

Answer

To understand why \( NH_3 \) has a much higher boiling point than \( PH_3 \), we can analyze the molecular properties and interactions of these compounds step by step.

### Step-by-Step Solution:

1. **Molecular Structure**:
- \( NH_3 \) (Ammonia) consists of nitrogen (N) bonded to three hydrogen (H) atoms.
- \( PH_3 \) (Phosphine) consists of phosphorus (P) bonded to three hydrogen (H) atoms.

2. **Electronegativity**:
- Nitrogen is more electronegative than phosphorus. This means that nitrogen attracts the bonding electrons more strongly than phosphorus does.
- The electronegativity of nitrogen leads to a significant dipole moment in \( NH_3 \), which contributes to stronger intermolecular forces.

3. **Hydrogen Bonding**:
- Due to the high electronegativity of nitrogen, \( NH_3 \) can form hydrogen bonds between its molecules. Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine.
- In contrast, \( PH_3 \) does not form hydrogen bonds because phosphorus is less electronegative and does not create a significant dipole moment.

4. **Intermolecular Forces**:
- The presence of hydrogen bonds in \( NH_3 \) leads to stronger intermolecular forces compared to the weaker van der Waals forces present in \( PH_3 \).
- Stronger intermolecular forces require more energy to overcome, resulting in a higher boiling point for \( NH_3 \).

5. **Boiling Points**:
- The boiling point of \( NH_3 \) is significantly higher than that of \( PH_3 \) due to the hydrogen bonding present in \( NH_3 \) which is absent in \( PH_3 \).

### Conclusion:
Thus, the reason \( NH_3 \) has a much higher boiling point than \( PH_3 \) is that \( NH_3 \) forms hydrogen bonds, while \( PH_3 \) does not.