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### Kc vs K

Posted: Tue Jan 07, 2020 4:44 pm
Is there a difference between Kc and K? I couldn't figure out if there was a difference or not in the textbook.

### Re: Kc vs K

Posted: Tue Jan 07, 2020 4:49 pm
In the book, they seem to use K for pressure. While the "c" in Kc stands for concentration. So it is used when we use concentration as opposed to pressure to calculate K.

### Re: Kc vs K

Posted: Tue Jan 07, 2020 6:12 pm
K or Kp is used when there are gases in the chemical equation, unless stated otherwise because gases can be discussed in terms of molar concentration. Meanwhile, Kc is for concentrations in mol/L for solutes in a condensed phase.

### Re: Kc vs K

Posted: Thu Jan 09, 2020 12:27 pm
Alexis Webb 2B wrote:K or Kp is used when there are gases in the chemical equation, unless stated otherwise because gases can be discussed in terms of molar concentration. Meanwhile, Kc is for concentrations in mol/L for solutes in a condensed phase.

Hi,

I was wondering if you could explain why gases would be discussed in molar concentration, and if partial pressures should be in atm for Kp. Thank you!

### Re: Kc vs K

Posted: Thu Jan 09, 2020 12:31 pm
DHavo_1E wrote:
Alexis Webb 2B wrote:K or Kp is used when there are gases in the chemical equation, unless stated otherwise because gases can be discussed in terms of molar concentration. Meanwhile, Kc is for concentrations in mol/L for solutes in a condensed phase.

Hi,

I was wondering if you could explain why gases would be discussed in molar concentration, and if partial pressures should be in atm for Kp. Thank you!

Hi,
If all of the species in a reaction is in gaseous form, you can use partial pressure to solve for Kp. You can use any units for solving with partial pressure as long as it remains consistent, e.g. using all atm or all bar.

### Re: Kc vs K

Posted: Thu Jan 09, 2020 12:39 pm
Kc is used when calculating the equilibrium constant using concentration, whereas Kp is used for calculating the equilibrium constant using partial pressure. However, as Dr. Lavelle explained in lecture, K can be used as an abbreviation to represent either Kc or Kp, depending on the context of the problem.

### Re: Kc vs K

Posted: Thu Jan 09, 2020 2:48 pm
K can be used to abbreviate for either Kc or Kp.