## When to use Kc vs Kp

Timmy Nguyen Dis 1I
Posts: 107
Joined: Sat Aug 17, 2019 12:17 am

### When to use Kc vs Kp

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

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

Aiden Metzner 2C
Posts: 104
Joined: Wed Sep 18, 2019 12:21 am

### Re: When to use Kc vs Kp

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

JohnWalkiewicz2J
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Joined: Thu Jul 11, 2019 12:17 am
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### Re: When to use Kc vs Kp

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
Posts: 105
Joined: Sat Jul 20, 2019 12:16 am

### Re: When to use Kc vs Kp

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.

Posts: 97
Joined: Tue Feb 12, 2019 12:15 am

### Re: When to use Kc vs Kp

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
Posts: 108
Joined: Sat Sep 07, 2019 12:18 am

### Re: When to use Kc vs Kp

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

AGaeta_2C
Posts: 112
Joined: Wed Sep 18, 2019 12:21 am

### Re: When to use Kc vs Kp

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.