Question

The intermolecular forces that exist among the molecules of NH₃ gas are:

A. dipole-dipole forces only.
B. London dispersion forces only.
C. both dipole-dipole and London dispersion forces.
D. neither dipole-dipole nor London dispersion forces.

Answer 1

The intermolecular forces among NH₃ gas molecules are hydrogen bonds.

Step-by-step explanation:

The intermolecular forces that exist among the molecules of NH₃ gas are neither dipole-dipole nor London dispersion forces.

Intermolecular forces are electrostatic in nature and include van der Waals forces and hydrogen bonds. The three major types of intermolecular interactions are dipole-dipole interactions, London dispersion forces, and hydrogen bonds. Dipole-dipole interactions arise from the electrostatic interactions of the positive and negative ends of molecules with permanent dipole moments. London dispersion forces are due to the formation of instantaneous dipole moments in molecules as a result of fluctuations of electron charge distribution. Hydrogen bonds are especially strong dipole-dipole interactions between molecules that have hydrogen bonded to a highly electronegative atom.

In the case of NH₃ gas, the intermolecular forces are hydrogen bonds. The nitrogen atom in NH₃ is partially positively charged, and the hydrogen atoms are partially negatively charged. The hydrogen atoms can form hydrogen bonds with the lone pairs of electrons on neighboring nitrogen atoms. This results in attractive forces between NH₃ molecules.