Sep 2, 2010
280
0
Status
Podiatry Student
EDIT: Yikes! Cant change the title. I meant boiling point not melting point

Hey guys. I got this question wrong on AAMC #4. Check out the screenshot.

It is part of a passage but IMO doesnt really have anything to do with it.

Edit: deleted pic. Sorry didn't know that was not allowed

Why is that the correct answer?

Logically I would imagine that the reason is either because O2 is more electronegative and thus can H bond more easily or because N2 has 3 bonds making it harder to break apart.
 
Last edited:

WhiteWashed

10+ Year Member
7+ Year Member
Mar 26, 2008
145
0
Status
Pre-Medical
EDIT: Yikes! Cant change the title. I meant boiling point not melting point

Hey guys. I got this question wrong on AAMC #4. Check out the screenshot.

It is part of a passage but IMO doesnt really have anything to do with it.



Why is that the correct answer?

Logically I would imagine that the reason is either because O2 is more electronegative and thus can H bond more easily or because N2 has 3 bonds making it harder to break apart.
While O2 is more electronegative, these are diatomic molecules with Pure covalent bonds...electronegative should not be considered.

Just a general trend, higher molecular weight=higher boiling point because of increased LDFs....correct me if i'm wrong.
 

phltz

7+ Year Member
May 13, 2010
889
30
Status
Medical Student
I'm pretty sure having this screenshot here can get you into trouble. AMCAS is pretty uptight about keeping its tests under wraps.

That said, the O=O bond is non-polar, because O is just as electronegative as O. Likewise the bonds in nitrogen are non-polar. Polar molecules generally have a higher BP, but these are both equivalently non-polar, so that's a wash.

Reactivity is a red herring, because the process of boiling doesn't involve any chemical reactions.

Triple vs. double bonds would only really be relevant if those bonds were involved in some sort of a reaction. So that's also irrelevant.

All else being equal, bigger, heavier molecules tend to have a higher BP. This is a small effect, but given that there's no other distinguishing characteristics, its enough to account for a (slight) difference in BPs.

Your idea about hydrogen bonding is irrelevant, because there are no hydrogens anywhere in this question, so no hydrogen bonding can take place. Your idea about triple bonds is incorrect because boiling does not involve breaking any bonds within a given molecule (like the bonds between the two N atoms in a diatomic nitrogen molecule), it just means your moving the molecules further apart. Boiling doesn't break N molecules apart.