Which is the predominant intermolecular force present in liquid ammonia (NH_3)?

• A. London dispersion forces
• B. Hydrogen bonding
• C. Dipole-dipole interactions
• D. Ion-dipole interactions

Answer: (B)

Verified step by step guidance

1. Identify the molecular structure of ammonia (NH_3). Ammonia has a trigonal pyramidal shape with nitrogen bonded to three hydrogen atoms and a lone pair on nitrogen.
2. Determine the polarity of the molecule. Because nitrogen is more electronegative than hydrogen, the N-H bonds are polar, and the molecule has a net dipole moment, making it polar.
3. Recall the types of intermolecular forces: London dispersion forces (present in all molecules), dipole-dipole interactions (between polar molecules), hydrogen bonding (a special, stronger type of dipole-dipole interaction involving H bonded to N, O, or F), and ion-dipole interactions (between ions and polar molecules).
4. Check if hydrogen bonding is possible. Since ammonia has hydrogen atoms directly bonded to nitrogen (a highly electronegative atom), it can form hydrogen bonds with neighboring ammonia molecules.
5. Conclude that the predominant intermolecular force in liquid ammonia is hydrogen bonding, which is stronger than regular dipole-dipole interactions and London dispersion forces in this case.