Treating Systems that have Small Equilibrium Constants

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sboutros2B
Posts: 24
Joined: Sat Jul 09, 2016 3:00 am

Treating Systems that have Small Equilibrium Constants

Postby sboutros2B » Tue Nov 22, 2016 7:04 pm

Hi Chem community!
I apologize in advance if this has been posted/answered. I'm just a little confused on why we can approximate when solving for equilibrium concentrations if K is super small.
Thank you very much (:

Anjum Farook 2O
Posts: 25
Joined: Wed Sep 21, 2016 2:59 pm

Re: Treating Systems that have Small Equilibrium Constants

Postby Anjum Farook 2O » Tue Nov 22, 2016 8:06 pm

hi! this helped me sort of gauge when we can/can't approximate and why:

https://www.khanacademy.org/science/che ... r-small-kc

sboutros2B
Posts: 24
Joined: Sat Jul 09, 2016 3:00 am

Re: Treating Systems that have Small Equilibrium Constants

Postby sboutros2B » Wed Nov 23, 2016 4:13 pm

this was so helpful thank you so so much!

Minu Reddy
Posts: 31
Joined: Sat Jul 09, 2016 3:00 am

Re: Treating Systems that have Small Equilibrium Constants

Postby Minu Reddy » Tue Nov 29, 2016 12:46 am

I'm so sorry if this question has already been asked. But am I correct in remembering that Dr. Lavelle mentioned if the k value is less than 10^-4 then it is ok to approximate? Or do you just have to look at if the value of x is less than 5% of the initial concentration?

Thank you!

Jared Gao 3G
Posts: 16
Joined: Wed Sep 21, 2016 2:58 pm

Re: Treating Systems that have Small Equilibrium Constants

Postby Jared Gao 3G » Tue Nov 29, 2016 2:12 pm

I can't remember whether Lavelle mentioned 10^-4 as a cut off for being able to approximate, but in the video posted above, the lecturer does go over it and says when Kc is less than or equal to 10^-4, we can approximate x to be a very small number and use the approximation method.


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