Question

Which substance has the higher boiling point? Why? HF or CO.

A) HF; it forms hydrogen bonds
B) CO; it has a larger molecular weight
C) HF; it has a smaller molecular weight
D) CO; it has weaker intermolecular forces

Answer 1

HF has a higher boiling point than CO because it can form strong hydrogen bonds, which are a powerful type of dipole-dipole interaction considerably influencing the substance's boiling point.

Step-by-step explanation:

The substance with the higher boiling point between HF (hydrogen fluoride) and CO (carbon monoxide) is HF due to its ability to form hydrogen bonds. These hydrogen bonds are particularly strong forms of dipole-dipole interactions that arise when hydrogen is bonded to highly electronegative atoms like fluorine, oxygen, or nitrogen. HF can form two hydrogen bonds at a time, which dramatically increases its boiling point compared to CO, which is a nonpolar molecule with much weaker London dispersion forces as its primary intermolecular force.

Regarding the options provided: A) HF; it forms hydrogen bonds is the correct answer. While molecular weight can influence boiling points, as seen with larger nonpolar molecules, the attraction due to hydrogen bonding in HF greatly exceeds any effect that molecular weight could have in this comparison. Therefore, the considerable difference in the strength of intermolecular forces, not the molecular weight, is the reason for HF's higher boiling point over CO.