Using Kc Vs Kp

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Rodrigo2J
Posts: 87
Joined: Sat Jul 20, 2019 12:16 am

Using Kc Vs Kp

Postby Rodrigo2J » Thu Jan 09, 2020 4:50 pm

When a question asks us to identify the equilibrium expression for K, can we use either Kp (use partial pressures for the expression) or Kc (use concentrations for the expression)? or do we have to use a specific one in certain situations?

Astrid Lunde 1I
Posts: 88
Joined: Sat Sep 07, 2019 12:16 am

Re: Using Kc Vs Kp

Postby Astrid Lunde 1I » Thu Jan 09, 2020 4:55 pm

The units in the question should help you find out when to use Kc and Kp. Kc is in M and Kp is in Bar.

Kallista McCarty 1C
Posts: 180
Joined: Wed Sep 18, 2019 12:18 am

Re: Using Kc Vs Kp

Postby Kallista McCarty 1C » Thu Jan 09, 2020 5:19 pm

You should be able to tell based on the question that is being asked!

805307623
Posts: 81
Joined: Fri Aug 09, 2019 12:17 am

Re: Using Kc Vs Kp

Postby 805307623 » Thu Jan 09, 2020 5:30 pm

It might be helpful to pay close attention to the chemical equation and see if the molecules being used are identified as (l),(g),(aq).

Edmund Zhi 2B
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Joined: Sat Jul 20, 2019 12:16 am

Re: Using Kc Vs Kp

Postby Edmund Zhi 2B » Fri Jan 10, 2020 5:35 pm

I believe you should look at the states of matter and try and determine from that

Megan Cao 1I
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Joined: Sat Sep 07, 2019 12:18 am

Re: Using Kc Vs Kp

Postby Megan Cao 1I » Fri Jan 10, 2020 11:18 pm

Kc is generally used when you're given molar concentrations of solutions and Kp is generally used when you're given partial pressures.

faithkim1L
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Joined: Fri Aug 09, 2019 12:17 am

Re: Using Kc Vs Kp

Postby faithkim1L » Fri Jan 10, 2020 11:48 pm

Kp is used for gases. Kc can be used for aqueous solutions. It's best to just go by the equation. Remember Kp is in pressure units and Kc is for concentration (M).

Shail Avasthi 3C
Posts: 86
Joined: Fri Aug 30, 2019 12:17 am

Re: Using Kc Vs Kp

Postby Shail Avasthi 3C » Sat Jan 11, 2020 8:54 pm

If you're looking at aqueous equilibrium, use Kc. If looking at gasses, you can either use Kc or Kp. Use the question to determine the proper answer.

Eva Zhao 4I
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Joined: Sun Sep 29, 2019 12:16 am

Re: Using Kc Vs Kp

Postby Eva Zhao 4I » Tue Jan 21, 2020 10:09 am

Kp can only be used when reactants and products are gases. Kc can be used for gases or aqueous substances, but you should check the units involved to ensure you're using the right K.

205291012
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Joined: Mon Nov 11, 2019 12:17 am

Re: Using Kc Vs Kp

Postby 205291012 » Tue Jan 21, 2020 11:16 pm

This depends on the information given in the question. I believe even if the molar concentrations of gases is given then you would just calculate Kc. But if the partial pressures are given then calculate Kp.

Mariah
Posts: 78
Joined: Fri Aug 02, 2019 12:16 am

Re: Using Kc Vs Kp

Postby Mariah » Wed Jan 22, 2020 4:18 pm

It just depends on what is given at the beginning and what is being asked for.

bellaha4F
Posts: 89
Joined: Wed Sep 18, 2019 12:20 am

Re: Using Kc Vs Kp

Postby bellaha4F » Wed Jan 22, 2020 6:08 pm

if all the components are gases, use kp. if all aqueous, use kc. (unless the test question says otherwise)

Kristina Rizo 2K
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Joined: Wed Sep 18, 2019 12:19 am

Re: Using Kc Vs Kp

Postby Kristina Rizo 2K » Thu Jan 23, 2020 6:01 pm

I know the units for Kc is molarity, but could someone give the units to know if it is partial pressure.

Leonardo Le Merle 1D
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Joined: Wed Feb 27, 2019 12:16 am

Re: Using Kc Vs Kp

Postby Leonardo Le Merle 1D » Fri Jan 24, 2020 12:29 pm

There is no unit for Kc or Kp, it is simply a value used to represent the ratio of product and reactant concentration at equilibrium

705367472
Posts: 22
Joined: Tue Nov 19, 2019 12:19 am

Re: Using Kc Vs Kp

Postby 705367472 » Sun Jan 26, 2020 9:20 pm

When trying to find Kc or Kp you would use the same equation of product over reactants just like finding Q?

605395381
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Joined: Mon Jun 17, 2019 7:24 am

Re: Using Kc Vs Kp

Postby 605395381 » Sun Jan 26, 2020 9:23 pm

It would depends on the chemical equation given

vanessas0123
Posts: 83
Joined: Wed Sep 11, 2019 12:17 am

Re: Using Kc Vs Kp

Postby vanessas0123 » Tue Jan 28, 2020 10:21 am

You use Kc when given concentrations, and Kp when given partial pressures.

Trent Yamamoto 2J
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Joined: Sat Aug 17, 2019 12:18 am

Re: Using Kc Vs Kp

Postby Trent Yamamoto 2J » Tue Jan 28, 2020 1:48 pm

You would use Kc when given molar concentrations of solutions in any state and Kp when you're given partial pressures only in the gas state

kennedyp
Posts: 31
Joined: Tue Nov 13, 2018 12:18 am

Re: Using Kc Vs Kp

Postby kennedyp » Thu Jan 30, 2020 5:14 pm

If you are given concentrations, then you should use Kc. If you are given gases, then you should use Kp.


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