explain how a solution containing 0.10 m acetic acid (hc2h3o2) and 0.10 m sodium acetate (nac2h3o2) can resist changes in ph when small amounts of either hcl or naoh are added. the sodium acetate/acetic acid solution is an example of a buffer. it contains appreciable quantities of both a weak acid (acetic acid) and its conjugate base (acetate ion.) the buffer resists changes in ph by removing the ---select--- ions that dissociate from an added strong acid or the ---select--- ions that dissociate from an added strong base. added strong acid reacts with some of the ---select--- in the buffer, and the added strong base reacts with some of the ---select--- in the buffer.