The Chemical kinetic equilibrium of a reaction is not a specific single state, but a particular dynamic equilibrium that is achieved when the rates of the forward and reverse reactions become equal.
Consider the elementary reversible reaction
A + B = R +S
Rate of formation of R by forward reaction.
r_R = K_1 C_A C_B
Rate of disabler of R by reverse reaction
-r_R = K_2 C_R C_S
At equilibrium, the rate of formation of R is zero
r_R Forword + r_R Revers = 0
K_1 C_A C_B - K_2 C_R C_S
K_1 C_A C_B = K_2 C_R C_S
K_1 / K_2 = (C_A C_B) / (C_R C_S)
We know that K_1 / K_2 = K_c
K_c = (C_A C_B) / (C_R C_S)
But at equilibrium
K_c = K_1 / K_2
From the point of view of chemical kinetics, the system will be in equilibrium if the rates of change of the forward and reverse elementary reactions are equal.
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