Question

Methane (molar mass 16.04 g/mol) boils at -164°C. Water has almost the same molar mass (18.02 g/mol), but boils at 100°C. Which of the following BEST explains the reason for the large discrepancy in boiling point?

A. Methane is ionic and, therefore, has a lower boiling point.

B. Water is ionic and, therefore, has a higher boiling point.

C. Both compounds only exhibit van der Waals forces.

D. Both compounds are polar. Water is more polar than Methane .

E. Water exhibits hydrogen bonding.

F. Methane exhibits hydrogen bonding.

Answer 1

Answers (B) and (E) are best reasons for this discrepancy.

Boiling point is mainly depends upon intermolecular forces between molecules. These forces are several types. Among all hydrogen bonding and dipole diplole interactions are strong. Vandewaal forces are very weak. In metahane vanderwaal forces exist. So it has low boiling point. In water hydrogen bonding is present between molecules, so it has high boiling point. In addition to this, water is highly polar in nature due to electronegative difference between oxygen and hydrogen. So as polarity is more, the dipole- dipole interactions are increased.