Kc and Kp

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Shirley Liu 2I
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Joined: Fri Sep 28, 2018 12:16 am

Kc and Kp

Postby Shirley Liu 2I » Sun Jan 13, 2019 3:38 pm

Kp is used for when all the products and reactants are in gas phase. However, could we also use Kc for reactions where everything is in gas phase? Would you use PV=nRT to convert between pressure and concentration then?

Hovik Mike Mkryan 2I
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Joined: Fri Sep 28, 2018 12:25 am

Re: Kc and Kp

Postby Hovik Mike Mkryan 2I » Sun Jan 13, 2019 3:44 pm

I believe calculating concentration for a reaction in all gas phase is used with the PV=nRT formula.Hope this helps!

Raquel Ruiz 1K
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Joined: Tue Nov 14, 2017 3:02 am

Re: Kc and Kp

Postby Raquel Ruiz 1K » Sun Jan 13, 2019 3:46 pm

Yes you can use Kc when everything is in gas phase. It makes calculations easier, and you won't have to convert back and forth from Kp to Kc or Kc to Kp. And yes we would have to use pV=nRT to convert. Remember that concentration= n/V

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Re: Kc and Kp

Postby Abby-Hile-1F » Sun Jan 13, 2019 3:50 pm

Kc can be used for both aqueous and gasphases, but Kp is for gases since you use pressure. And the ideal gas law can be used to relate Kp and Kc

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Re: Kc and Kp

Postby 804994652 » Mon Jan 14, 2019 7:16 pm

Does 'K' most often refer to Kp or Kc?

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Re: Kc and Kp

Postby marisaimbroane1J » Mon Jan 14, 2019 7:30 pm

@804994652 , K can refer to either one and does not refer to one "more often". Either Kc or Kp can be written as just a general K as well; it is just important to use the information given in the problem to find the one asked for or that is easier to find using the given information.

Elisa Bass 4L
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Joined: Fri Sep 28, 2018 12:23 am

Re: Kc and Kp

Postby Elisa Bass 4L » Mon Jan 14, 2019 7:36 pm

According to the textbook, technically if you are asked for K and everything is in gas phase, you’re supposed to write it with partial pressures. However, the problem will likely specify which they are looking for, or will give values in concentration or partial pressure. In the event they give you something in the gas phase and something that is aqueous, for example, always use concentration.

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