Hello,
The formula of equilibrium constant depends on the reaction.
For a general reaction:
aA + bB = cC + dD
The equilibrium constant (Kc) is:
Kc = (C power c × D power d) / (A power a × B power b)
Here, the concentrations of products are in the numerator and reactants are in the denominator, each raised to their coefficients.
For gases, we use Kp based on partial pressures.
I hope this helps you.