Buffers are characterized by pH and capacity. Acetic acid plus one-half equivalent of sodium hydroxide.
Sodium acetate plus one-half equivalent of sodium hydroxide.
Well, the solution has an acid and a base component. However, the common-ion effect is not going to help the solution to maintain a nearly constant pH when acid or base is added. A strong acid would react with acetate while a strong base would react with formic acid. However, both equilibria affect pH independently of the other component, so that together they do not make an effective buffer. Indicators Indicators are useful for characterizing pH and for use in titrations to determine the concentrations of unknown acids or bases.