When to use Kc vs Kp

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Timmy Nguyen Dis 1I
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Joined: Sat Aug 17, 2019 12:17 am

When to use Kc vs Kp

Postby Timmy Nguyen Dis 1I » Sun Jan 12, 2020 3:42 pm

As title implies, when do we use each one? Do we use (aq) in Kp? Do we use (g) in Kc?

AKhanna_3H
Posts: 104
Joined: Wed Sep 18, 2019 12:19 am

Re: When to use Kc vs Kp

Postby AKhanna_3H » Sun Jan 12, 2020 3:46 pm

Kc refers to concentrations and Kp refers to pressure, so (aq) would correlate to Kc and (g) to Kp

Aiden Metzner 2C
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Re: When to use Kc vs Kp

Postby Aiden Metzner 2C » Sun Jan 12, 2020 3:47 pm

We use Kp when calculating partial pressure of gases and Kc when calculating concentration of aqueous solutions.

JohnWalkiewicz2J
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Re: When to use Kc vs Kp

Postby JohnWalkiewicz2J » Sun Jan 12, 2020 4:02 pm

Typically you would use Kp when dealing with reactants and products that are both in the gas state(g).
You would using Kc when dealing with reactants and products that are both in an aqueous(aq) state.

Hope this helps! : )

Julie_Reyes1B
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Joined: Sat Jul 20, 2019 12:16 am

Re: When to use Kc vs Kp

Postby Julie_Reyes1B » Sun Jan 12, 2020 4:08 pm

It’s also important to keep in mind that when you have a mix of both aqueous solutions and gases, you may have to convert partial pressure to concentration. You can do this by rearranging PV=nRT. You would then use Kc to calculate the equilibrium constant.

Radha Patel 4I
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Re: When to use Kc vs Kp

Postby Radha Patel 4I » Sun Jan 12, 2020 4:14 pm

kc refers to aqueous solutions and kp refers to the gas phase. One thing to highlight is that when you use kc, the general way to indicate that it is an aqueous solution is with brackets ( kc= [P]/[R] ) and with kp you indicate it with parentheses ( kp=(P)/(R) )

chari_maya 3B
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Re: When to use Kc vs Kp

Postby chari_maya 3B » Sun Jan 12, 2020 5:38 pm

what would happen if the reactant(s) and/or products are different states?

AGaeta_2C
Posts: 112
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Re: When to use Kc vs Kp

Postby AGaeta_2C » Sun Jan 12, 2020 8:15 pm

chari_maya 3B wrote:what would happen if the reactant(s) and/or products are different states?

If the R or P are in different states, you calculate Kc, since aqueous and gaseous solutions exist in concentrations.
You really only calculate Kp when all the R and P are gaseous, but even then, it is generally acceptable to calculate Kc.


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