Chapter 8, Problem 8.51PAE

Interpretation Introduction

Interpretation:

The observations that carbon tetrachloride $\left({\text{CCl}}_{\text{4}}\right)$ is liquid and ammonia $\left({\text{NH}}_{\text{3}}\right)$ is a gas at room temperature and pressure should be rationalized.

Concept Introduction:

Polar molecules have more boiling point due to partial ionic character between the ions. Net polarity is dependent on the structure of the molecule as, a molecule with atoms with electronegativity difference can be non-polar if all the dipole moments get cancelled out.

Carbon tetrachloride has a symmetrical tetrahedral structure in which the central carbon atom is attached to four chlorine atoms. Each $\text{C}-\text{Cl}$ bond has polarity, but the net polarity of the compound is cancelled due to the symmetrical structure of the compound. For this reason, carbon tetrachloride is a non-polar covalent compound.

Ammonia has a trigonal pyramidal structure in which the central nitrogen atom is attached to three hydrogen atoms. The molecule shows a net polarity, due to the polarity of each $\text{N}-\text{H}$ bond. For this reason, ammonia is a polar covalent compound.