Match each of the following chemical species with the predominant intermolecular force ope… — JAMB UTME

Match each of the following chemical species with the predominant intermolecular force operating between its molecules in the liquid or solid state.

Hydrogen fluoride ( $HF$ )Hydrogen bonding
Trichloromethane ( $CHCl_3$ )Permanent dipole-dipole interactions
Solid iodine ( $I_2$ )London dispersion forces (in a non-polar crystalline lattice)
Methane ( $CH_4$ )Weak London dispersion forces (in a small non-polar molecule)

Answer

Hydrogen fluoride matches with Hydrogen bonding; Trichloromethane matches with Permanent dipole-dipole interactions; Solid iodine matches with London dispersion forces (in a non-polar crystalline lattice); Methane matches with Weak London dispersion forces (in a small non-polar molecule).

Hydrogen fluoride forms hydrogen bonds due to the extreme electronegativity difference between H and F. Trichloromethane exhibits permanent dipole-dipole attractions because of its permanent net molecular dipole. Solid iodine is non-polar but has a large polarizable electron cloud leading to substantial London dispersion forces in its solid crystal. Methane is non-polar and small, possessing only weak London dispersion forces.

Step-by-Step Solution

Analyze the polarity and chemical structure of each given substance.

HF

is highly polar with

H-F

bonds;

CHCl_3

is a polar asymmetrical molecule;

I_2

is a non-polar diatomic solid;

CH_4

is a non-polar tetrahedral gas.

Intermolecular forces depend strictly on molecular polarity, presence of

N-H

O-H

, or

F-H

bonds, and molecular size/polarizability.

Identify specific conditions for hydrogen bonding.

HF

satisfies the requirement of hydrogen attached to highly electronegative fluorine, giving rise to intermolecular hydrogen bonds.

Hydrogen bonding requires a hydrogen atom covalently bonded to

N

O

, or

F

interacting with a lone pair on a neighbouring electronegative atom.

Differentiate dipole-dipole forces from dispersion forces in neutral covalent compounds.

CHCl_3

possesses a permanent dipole moment giving dipole-dipole forces, while

I_2

and

CH_4

are non-polar and rely on London dispersion forces, with

I_2

having larger dispersion forces due to greater electron cloud polarizability.

Dispersion forces scale with molecular size and electron count, while dipole-dipole forces require permanent polar bonds in asymmetrical shapes.

Key Concept

Classification and Origin of Intermolecular Forces

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