## Chemistry and Chemical Reactivity (9th Edition)

Every good buffer needs: 1. A weak acid. (a): $CH_3CO_2H$; (b): Missing; (c): $CH_3CO_2H$ and $HCO_2H$; (d): Missing; 2. The conjugate base of the weak acid (or a salt that contains it): (a): $KCH_3CO_2H$; (c): Missing; 3. They have to be in similar concentrations: (a) $0.20M$ $KCH_3CO_2$ and $0.20M$ $CH_3CO_2H$; Therefore, the correct answer is (a);