An acidic buffer solution is prepared by mixing a weak acid and its salt with a strong base .

• $CH_3COOH$, $H_2CO_3$, and $H_3PO_4$ are all weak acids, and their corresponding sodium salts will form acidic buffer solutions.
• $HClO_4$ (perchloric acid), on the other hand, is a very strong acid . A mixture of a strong acid and its salt does not act as a buffer solution. Therefore, $HClO_4$ and $NaClO_4$ is not an acidic buffer.