Chemical Equilibrium

Chemical reactions, much like the physical processes above, gradually settle into a state of equilibrium given enough time. Consider a general reversible reaction

Initially, only A and B are present, so the reaction runs almost entirely in the forward direction, and a few molecules of the products C and D start to appear. As the concentration of C and D builds up, more of these product molecules collide and react with each other in the backward direction, so the rate of the backward reaction keeps rising. At the same time, as A and B are used up, the rate of the forward reaction keeps falling. Eventually the two rates become equal -- and from that p …