However, as the reaction begins to proceed, the concentration of X begins to decrease, while the concentration of Y begins to increase because some of this X is converting or becoming Y. Eventually a point is reached in which the concentration of the reactants of X and the concentration of the products Y does not change. And this is known as chemical equilibrium. This is the point of greatest entropy. In other words, our entropy of our system is at its highest at equilibrium. Now, let's look at the rates of the reactions, the four reaction and the reverse reaction at each point.