Question

Describe what intermolecular forces are there in each of the following molecules and rank them in decreasing order of boiling point.

Cl-Cl, H-H, N $\equiv$ N, Br-Br, F-F

Answer 1

Each of the given molecules Cl₂ , H₂ , N₂ , Br₂ and F₂ are diatomic molecules which have London dispersion forces (or weak forces) as the only intermolecular forces present.

The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes called an induced dipole-induced dipole attraction.

Since each of the given molecules has same intermolecular forces present, therefore, boiling point depends upon molecular mass of because higher the mass, higher will be the attractive forces and more energy is required to break the interactions which increases the boiling point.

Highest boiling point : Br-Br > Cl-Cl > F-F > N $\small \equiv$ N > H-H : Lowest boiling point