Question

Two liquids, n-pentane and 1-butanol, have nearly the same molecular weight, but significantly different temperature values. Why is there a difference between these two substances, based on their intermolecular forces?

temperature values? Do you mean boiling points?

We are trying to predict temperature changes caused by the evaporation of these two liquids and relate them to the strength of intermolecular forces of attraction.

Aren't you looking at vapor pressure here, which correlates rather well with boiling points? 1-butanol is an alcohol and has hydrogen bonding. Therefore, the intermolecular forces are stronger in 1-butanol than in n-pentane. As a result, the vapor pressusre of n-pentane is much higher than that of 1-butanol and the evaporative cooling effect of n-pentane should be much higher. Does that agree with your test results.

Well we were doing an experiment called evaporation and intermolecular attraction and i missed this question on the exam and don't understand where i was wrong because i thought that the pentane had a stronger force.

Answer 1

Alkanes have weaker intermolecular forces than alcohols because they have no hydrogen bonding, only dispersion forces.