To behave as an acid, the substance must lose a proton. Buffers Buffers are solutions that resist a change in pH upon addition of small amounts of an acid or base. Since acid-base reactions in aqueous solution involve the transfer of a proton from the acid to the base, a buffer must contain significant amounts of both an acid and a base. Now, we add sodium acetate. When we add the acetate ion, less of the acetic acid will dissociate.
Capacity depends on the amounts of acid and conjugate base in the solution.