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Topic: Effects of Temp & Ea on Equilibrium Constant  (Read 8250 times)

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Offline Astrokel

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Effects of Temp & Ea on Equilibrium Constant
« on: April 01, 2008, 10:05:14 AM »
Values of equilibrium constants such as Kp and Kc are affected by a change in temperature.

I understand a change in pressure/concentration would not affect equilibrium constants as the system will counteract the change (Le Chatelier)

Why then a change in temperature would not be counteract such that the value of constants remain the same?

I've goggle up and the website below is highly mathematics(im in grade 12th) and is there any other qualitative way to see why a change in temp cause a change in equilibrium constants?

http://www.science.uwaterloo.ca/~cchieh/cact/applychem/temp_eqlbm.html

I've read up somewhere that Ea affects the values of equilibrium constants as well, is that true?

Thanks  ;D

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Offline FeLiXe

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Re: Effects of Temp & Ea on Equilibrium Constant
« Reply #1 on: April 01, 2008, 11:20:03 AM »
when you change pressure the pressure equilibrium constant (Kp) stays the same but the system changes. the concentrations and the concentrations equilibrium constant (Kc) change.

i would say we are basically just lucky that there is this Kp which stays constant over pressure and you cannot expect to find something like that for every quantity
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Offline Yggdrasil

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Re: Effects of Temp & Ea on Equilibrium Constant
« Reply #2 on: April 01, 2008, 05:45:30 PM »
Changing the activation energy of a reaction does not change the equilibrium constant.  Remember, the equilibrium constant depends on the thermodynamics of the reaction (i.e. it is dependent on ΔG).  ΔG is a state function meaning that the difference in free energy between products and reactants is the same no mater what path you take to go from reactants to products.

Ea, however, is a quantity that describes the path you take from reactants to products.  However, changing Ea does not change the identify of the reactants and products, so the overall ΔG of the reaction stays the same.  Since ΔG is the same, the equilibrium constant must also be the same.

Offline Astrokel

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Re: Effects of Temp & Ea on Equilibrium Constant
« Reply #3 on: April 04, 2008, 09:57:04 PM »
Changing the activation energy of a reaction does not change the equilibrium constant.  Remember, the equilibrium constant depends on the thermodynamics of the reaction (i.e. it is dependent on ΔG).  ΔG is a state function meaning that the difference in free energy between products and reactants is the same no mater what path you take to go from reactants to products.

Ea, however, is a quantity that describes the path you take from reactants to products.  However, changing Ea does not change the identify of the reactants and products, so the overall ΔG of the reaction stays the same.  Since ΔG is the same, the equilibrium constant must also be the same.

Thanks Yggdrasil,

So can i say equilibrium constant are dependent on ΔG and T?

Kelvin  :D
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Offline Yggdrasil

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Re: Effects of Temp & Ea on Equilibrium Constant
« Reply #4 on: April 04, 2008, 11:02:43 PM »
So can i say equilibrium constant are dependent on ΔG and T?

Yes.

K = e-ΔGo/RT

Offline Astrokel

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Re: Effects of Temp & Ea on Equilibrium Constant
« Reply #5 on: April 05, 2008, 07:09:27 AM »
thanks Ygg!  :)

cheerz

kelvin  :)
No matters what results are waiting for us, it's nothing but the DESTINY!!!!!!!!!!!!

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