Balanced reaction: A(g) + 2B(g) ⇄ 4C(g) + D(g).
Kp = [C]⁴·[D] / [A]·[B]².
[A] - equilibrium concentration of reactant A.
[B] - equilibrium concentration of reactant B
[C] - equilibrium concentration of product C.
[D] - equilibrium concentration of product D.
The substances on the right side of the reaction are written at the top of the Kp expression and those on the left at the bottom.
