## Equilibrium Constant

Jarrett Peyrefitte 2K
Posts: 102
Joined: Sat Aug 24, 2019 12:16 am

### Equilibrium Constant

When do you write the equilibrium constant as Kc? and when do you write the equilibrium constant as Kp?

Brian Tangsombatvisit 1C
Posts: 119
Joined: Sat Aug 17, 2019 12:15 am

### Re: Equilibrium Constant

The equilibrium constant is written as Kc when you use the concentrations of the reactants and products in the formula, in mol/L. The equilibrium constant is written as Kp when you use the partial pressures instead of the concentrations for the equation. You cannot mix concentrations and partial pressures in the formula. You would usually use Kp when all the reactants and products are in the gas phase and the units are for gases. You can use PV=nRT if needed to convert the partial pressure of a gas to concentration (n/V) and vice versa.

Alexandra Bartolome 2H
Posts: 102
Joined: Sat Jul 20, 2019 12:17 am

### Re: Equilibrium Constant

You use Kc when given molar concentrations of reactants and products. You use Kp when dealing with the partial pressures of reactants and products, which are in the gas phase.

Connor Ho 1B
Posts: 102
Joined: Sat Aug 17, 2019 12:17 am

### Re: Equilibrium Constant

Kc is used when one or more of the products and reactants are in the aqueous phase.

Kp is used when one or more of the products and reactants are in the gaseous phase.

Miriam Villarreal 1J
Posts: 105
Joined: Sat Aug 17, 2019 12:16 am

### Re: Equilibrium Constant

Kc is the equilibrium constant specifically for concentrations and Kp is the equilibrium constant for partial pressures

Micah3J
Posts: 100
Joined: Tue Oct 08, 2019 12:16 am

### Re: Equilibrium Constant

When writing the formula for K, does it matter if you put the gases in brackets as well or how do you differentiate that it is a gas and not aqueous?

Katie Bart 1I
Posts: 104
Joined: Sat Aug 24, 2019 12:16 am

### Re: Equilibrium Constant

How do you know whether to use Kc/Kp versus simply K? What is the difference?

Jainam Shah 4I
Posts: 130
Joined: Fri Aug 30, 2019 12:16 am

### Re: Equilibrium Constant

Kc is the equilibrium constant that uses concentration and you typically use this expression when you deal with aqueous solutions or are given molarities. Kp is the equilibrium constant that uses partial pressure and you use it when one or more of your reactants or products is in the gas phase.

AysiaB1I
Posts: 12
Joined: Wed Sep 18, 2019 12:17 am

### Re: Equilibrium Constant

Kc is used when the concentrations are given in the question, and Kp is used when the partial pressures are given in the question. For Kp, the given amounts typically have a unit in pressure (i.e. bar) which helps distinguish between the two.