And second, we can use it to find the ratio of conjugate base to conjugate acid or the ratio of conjugate acid to conjugate base of our buffet system. Now let's see where this equation comes from. Let's derive it. But first, let's look at the reaction of an acid in an aqueous state with the water molecule in the liquid state. Well, what we get is a conjugate base in the acreage state and a conjugate acid in the aqueous states. So let's write the equilibrium constant expression for this reaction.