So the rate of formation of Es is given by this rate law, k one multiplied by the concentration of the enzyme multiplied by the concentration of the substrate. Now, what about the rate of dissociation? Well, here we have two equations that describe the dissociation. One dissociates into the product and the other one dissociates back into the enzyme and the substrate. So on the left side of the equation, we have one term. On the right side, we have two terms because we have these two reactions.