## What has greater residual entropy at 0K?

$\Delta U=q+w$

Sammy Thatipelli 1B
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### What has greater residual entropy at 0K?

The question I am confused about is what has greater residual entropy at 0K: NO or BF3?

For this question, do we look at the masses, or do we draw out the Lewis structures to figure out the answers?

Karen Ung 2H
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### Re: What has greater residual entropy at 0K?

Normally, if there are more elements or number of elements in a molecule, that has greater residual entropy, but generally, bigger molecules have greater residual entropy in which case you calculate the molar masses of each molecule to find which one is bigger.

Justin Lai 1C
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### Re: What has greater residual entropy at 0K?

Yes, you should draw out the lewis structures. If you do, you will see that NO is non-symmetric and has resonance. BF3 is symmetric and only has one configuration, so NO should have greater residual entropy.

Leah Savage 2F
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Joined: Fri Sep 29, 2017 7:06 am

### Re: What has greater residual entropy at 0K?

Does resonance automatically imply a lot of entropy? In actuality resonance structures aren't found multiple forms but just with bonds in between double and single bonds, so how would this increase entropy?

Justin Lai 1C
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: What has greater residual entropy at 0K?

Things to look for when comparing entropy. The following will usually have higher entropy:
Gases in larger volume>smaller volume
Gases>liquids>solids
Larger mass>smaller mass
Greater complexity>less complex

Justin Lai 1C
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: What has greater residual entropy at 0K?

I think NO has resonance meaning that there has multiple possible structures. So there are more possible structures for NO than for BF3 which is why there is more residual entropy.