Chapter 2, Problem 2.47P

Interpretation Introduction

(a)

Interpretation:

The dominant intermolecular force between a pair of helium atoms and a pair ${\text{H}}_{\text{2}}$ molecule is to be determined.

Concept introduction:

The dominant intermolecular interaction between non-polar molecules is called induced dipole-induced dipole interaction or London dispersion forces. In a molecule, electrons are constantly moving around, and at some instant in time, there may be more electrons on one side of the molecule than there are on the other. The extra electrons on that one side gives rise to instantaneous dipole which can alter the electron distribution on a second molecule by repelling or attracting nearby electrons. This instantaneous dipole is directly proportional to the number of electrons possessed by the molecule that is on the molar mass.

Interpretation Introduction

(b)

Interpretation:

Why ${\text{H}}_{\text{2}}$ has a higher boiling point than helium is to be explained.

Concept introduction:

The boiling point of a compound depends on the strength of the intermolecular forces that exist between molecules. Boiling point is the energy required to break the bonds to change the state of a given molecule. The molecules with more surface area require more energy to break the bonds than the molecules with less surface area.