Using Kc vs Kp

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Nathan Barger 3B
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Joined: Fri Sep 25, 2015 3:00 am

Using Kc vs Kp

Postby Nathan Barger 3B » Wed Nov 18, 2015 6:16 pm

When exactly do you use Kc and when exactly do you use Kp. Although I understand that if you are given molar concentrations you should use Kc and if you are given partial pressures you should use Kp but if a question asks to simply write the expression for the equilibrium constant for the reaction and no numbers or concentrations are given but the gas equation is given, which do I use? I thought we were supposed to simply use Kc but the answer given in the back says to use Kp. is this because the entire equation involves nothing but gases?

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Re: Using Kc vs Kp

Postby Chem_Mod » Thu Nov 19, 2015 12:00 am

If there are only gases then Kp is appropriate. You would only be able to use Kc if the total volume of the container were given.

Kiara Quinn 3B
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Joined: Sat Jul 09, 2016 3:00 am

Re: Using Kc vs Kp

Postby Kiara Quinn 3B » Wed Nov 09, 2016 8:28 pm

Would there be a case in which you would have to use both Kc and Kp at the same time?

Joshua Baysa 1J
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Joined: Wed Sep 21, 2016 2:59 pm

Re: Using Kc vs Kp

Postby Joshua Baysa 1J » Thu Nov 10, 2016 11:31 am

I don't think you would have to use both Kc and Kp simultaneously (at least for this class). I'm not 100% sure but it doesn't seem like it. However, there is a way to manipulate the formulas in order to get both Kc and Kp in the same equation

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