Chemical Equilibrium

A chemical reaction is in equilibrium when the rate of forward reaction equals the rate of backward reaction.

i.e. ΔG = 0
ΔA + bB  ⇌  cC + dD
According to the law of mass action
R₁ = K₁    [A]^a [B]^b
R₂ = K₂    [C]^c [D]^d

At equilibrium, R₁ = R₂

K1 [A]^a [B]^b = K₂ [C]^c [D]^d
K1 = [C]^c [D]^d
—      ———-
K2 = [A]^a [B]^b = Kc

[C]c [D]d
∴ Kc = ———
[A]^a [B]^b
Where Kc = equilibrium constant.