Using Kc Vs Kp

[Rodrigo2J]

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]

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]

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

[805307623]

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]

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

[Megan Cao 1I]

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

[faithkim1L]

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 2C]

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]

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

[205291012]

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]

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

[bellaha4F]

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

[Kristina Rizo 2K]

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]

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]

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

[605395381]

It would depends on the chemical equation given

[vanessas0123]

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

[Trent Yamamoto 2J]

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]

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

[Susanna Givan 2B]

Is there any main difference in terms of how you solve K for Kc versus Kp?

[Caelin Brenninkmeijer 1G]

Is there any main difference in terms of how you solve K for Kc versus Kp?

When calculating Kc, I believe you can use the [P]/[R] equation. You can also use PV=nRT when converting between Kc and Kp.

[Susan Chamling 1F]

We use Kc if the problem uses concentrations, but we use Kp if the problem provides partial pressures.

[Sam Wentzel 1F 14B]

It depends on the state of the materials given. If the chemical equation involves gases, usually partial pressures. If the chemical equation involves AQ state chemicals, then usually use concentrations.