Kp vs. Kc

[klarratt2]

When you have an equation where all of the products and reactants are gases, is there any advantage to using Kp over Kc (or vice versa)? Which is better to use?

[Kate Chow 4H]

Usually when you have all gasses in the reaction, you use Kp. There's not necessarily an advantage to either Kc or Kp. It often comes down to the information that is provided in the problem.

[kamalkolluri]

It usually depends on numbers you're given. Kp is generally used if all compounds are gases, but you can also use Kc if the numbers are given in mols and you know the volume of the flask. When writing the equilibrium expression it is usually better to use partial pressures and Kp.