## Kc vs K

Donna Nguyen 2L
Posts: 100
Joined: Sat Aug 24, 2019 12:17 am

### Kc vs K

Is there a difference between Kc and K? I couldn't figure out if there was a difference or not in the textbook.

Alicia Lin 2F
Posts: 83
Joined: Wed Sep 18, 2019 12:17 am

### Re: Kc vs K

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.

Alexis Webb 2B
Posts: 124
Joined: Thu Jul 11, 2019 12:15 am

### Re: Kc vs K

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.

DHavo_1E
Posts: 118
Joined: Sat Aug 17, 2019 12:17 am

### Re: Kc vs K

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!

Alice Ma 2K
Posts: 52
Joined: Wed Nov 13, 2019 12:26 am

### Re: Kc vs K

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.

Gabriella Bates 2L
Posts: 113
Joined: Thu Jul 11, 2019 12:15 am

### Re: Kc vs K

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.

pmokh14B
Posts: 107
Joined: Sat Aug 17, 2019 12:15 am

### Re: Kc vs K

K can be used to abbreviate for either Kc or Kp.

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