The molecular mass of butanol, c4h9oh, is 74.14; that of ethylene glycol, ch2 (oh) ch2oh, is 62.08, yet their boiling points are 117.2 c and 174 c, respectively. explain the reason for the difference

Ethylene glycol has a higher boiling point because it has more hydroxyl groups, and thus will form more H-bonds.

Explanation:

Generally, we say that the boiling point increases with higher molecular mass, because of increase of Van der waals forces.

In this case, we see that ethylene glycol has a lower molecular mass but higher boiling point.

The reason for this can be explained, when we look at the structure of both butanol and ethylene glycol.

Butanol has 1 hydroxyl-group, while ethylene glycol has 2 hydroxyl- groups.

Since ethylene glycol has more hydroxyl groups, it can also create more H-bonds.

The higher the amount of H-bounds the higher the boiling point. So ethylene glycol has a higher boiling point because it has more hydroxyl groups, and thus will form more H-bonds.