Thermodynamically Stable?

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Ellis Song 4I
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Joined: Thu Jul 11, 2019 12:17 am

Thermodynamically Stable?

Postby Ellis Song 4I » Tue Jan 14, 2020 11:05 pm

(a) In an experiment, 2.0 mmol Cl2(g) was sealed into a reaction vessel of volume 2.0 L and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 5G.2 to calculate the equilibrium composition of the mixture. (b) If 2.0 mmol F2 was placed into the reaction vessel instead of the chlorine,what would be its equilibrium composition at 1000. K? (c) Use your results from parts (a) and (b) to determine which is thermodynamically more stable relative to its atoms at 1000. K, Cl2 or F2.

I found in part a that the equilibrium concentration was 1.1x10^-5 and for part b it was 3.2x10^-4. Part c asks to determine which is more thermodynamically stable but what does that mean?

Caitlyn Tran 2E
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Joined: Fri Aug 09, 2019 12:15 am

Re: Thermodynamically Stable?

Postby Caitlyn Tran 2E » Tue Jan 14, 2020 11:19 pm

When something is more thermodynamically stable, it just means that it is less likely that it will dissociate since stable molecules want to stay the way they are. To figure out part c, where it asks which one is more stable, just look at whether chlorine gas or fluorine gas dissociates less. The one that dissociates less is more thermodynamically stable. Hope this helps!

Justin Vayakone 1C
Posts: 110
Joined: Sat Sep 07, 2019 12:19 am

Re: Thermodynamically Stable?

Postby Justin Vayakone 1C » Tue Jan 14, 2020 11:24 pm

Being thermodynamically stable means being in a low energy state. The less energy or enthalpy a molecule has, the more stable it is. Now to the problem, we are asked which reactant (Cl2 or F2) is more stable. The more stable a reactant is, the less it wants to dissociate into product. Comparing 1.1x10^-5 to 3.2x10^-4, we see the equilibrium concentration of Cl product is smaller, so we can say Cl2 is more stable than F2.

Justin Seok 2A
Posts: 104
Joined: Sat Aug 24, 2019 12:15 am

Re: Thermodynamically Stable?

Postby Justin Seok 2A » Tue Jan 14, 2020 11:52 pm

A thermodynamically stable thing tends to keep its form well. So when comparing Cl2 and F2, we simply look to see which of the two has a smaller equilibrium constant. Since Cl2 does, it is more thermodynamically stable, since a smaller ratio of Cl2 dissociates into Cl atoms compared to F2 and F atoms.

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