[Zoloft]

I had a lab on evaporative cooling, and I have several questions, among them: "Draw and describe the forces between two molecules of hexane."

Uhm, what kind of forces are the talkinga bout? Ionic? Covalent?

Furthermore, the instructor wasn't quite clear on how structural features are related to evaporative cooling.

relationship between intermolecular and molecular structure?

Any help is appreciated!

[typhoon2028]

Try thinking about van der Waals force or hydrogen bonding, for examples?


Take water for an example:  Why does a molecule of low molecular weight have sucha a high boiling point?  One thought is that the hydrogen & oxygen atoms are interacting by positive/negative attraction.  This requires more energy to break these bond attractions.


I might be mistaken but evaporative cooling, works with the latent heat of vaporization.  Typically, materials with large heat of vaporization have higher molecular forces (van der Waals force or hydrogen bonding).

[mreff555]

Hexane is non-polar. Well at least, mostly nonpolar. London dispersion, a particular type of Van der waals force, should be the biggest factor in the bonding of hexane molecules, hence the low boiling point. Smaller alkanes like ethane have even lower boiling points, because there are less carbons and therefore less places for partial charges to form.

Water is polar. The molecules are subject to Hydrogen bonding which can have bond energy's as high as 30kj/mol. Thats why it has a high bp

[typhoon2028]

I understand water is polar.  I was using it as an example of different molecular forces at work

[mreff555]

I'm sorry, I didn't mean to discredit you. I just was trying to make my point clear. I see what you were getting at.