Circle and clearly identify (name) two functional groups in this molecule. In Chemistry, you learned about the law of mass action and reactions at equilibrium. For the reaction P+QR+S, you can tell that P reacts with Q to form products R and S in the forward direction, and R reacts with S to form P and Q in the reverse direction. At equilibrium, the rates of the forward and reverse reactions are equal, so there is no net change in the amounts of P,Q,R, or S. (The actual amounts of P,Q,R, and S are not necessarily the same.)