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### Kp

Posted: Fri Jan 11, 2019 11:01 am
I understand that K is often used to represent either Kc or Kp and that they are found in the same manner. Why do we use Kp for gases when we could also use Kc? Is one more preferred than the other?

### Re: Kp

Posted: Fri Jan 11, 2019 11:07 am
As you probably know, K represents the equilibrium constant. The subscripts specify what the equilibrium constant consists of. Kc means the equilibrium constant of concentrations whereas Kp means the equilibrium constant of the partial pressures. You use Kp when the equation includes just gases just to be more specific. It shows that there are only gases. However, depending on the question, it may ask for Kc or simply K in which your answer will be okay either way.

### Re: Kp

Posted: Fri Jan 11, 2019 11:16 am
Additionally, when using Kp, partial pressure has to be calculated where when Kc is used, the concentrations have to be calculated

### Re: Kp

Posted: Fri Jan 11, 2019 12:02 pm
Neither Kp or Kc is preferred but often times Kp will be used when the reaction involves gases and ask for the partial pressure. If the question is asking for molar concentration automatically assume to use Kc. Also remember when using Kc use brackets which indicate concentration and for Kp use parentheses to indicate partial pressure. (When setting up to solve for either Kp or Kc)

### Re: Kp

Posted: Fri Jan 11, 2019 1:19 pm
Kp simply related to the equilibrium constant when everything reacting is a gas but the process of finding it is the same as the Kc equation.

### Re: Kp

Posted: Fri Jan 11, 2019 2:47 pm
I believe you can usually figure out whether or not to use Kp or Kc based on the information given surrounding the chemical equation because both can be used for gases but sometimes certain information is required depending on the K you are asked to use.

### Re: Kp

Posted: Fri Jan 11, 2019 3:39 pm
Kp and Kc are essentially the same. Kp is just used to specify that only gases are involved, and the p stands for partial pressure. Meanwhile Kc is in relation to equilibrium concentrations.

### Re: Kp

Posted: Fri Jan 11, 2019 4:14 pm
We sometimes use KP instead of KC for gases because that is what the problem gives us as the initial information.

### Re: Kp

Posted: Fri Jan 11, 2019 4:30 pm
The question should specify whether to solve for Kp or Kc.

### Re: Kp

Posted: Fri Jan 11, 2019 5:11 pm
Kp helps specify that the question is asking for partial pressures for gases instead of the equilibrium constant for concentrations.