 Thus, when there is an excess of ions in the solution carbonic acid "partially" neutralizes them by forming H2O and bicarbonate () ions.Similarly an excess of H+ ions is "partially" neutralized by the bicarbonate component of the buffer solution to form carbonic acid (H2CO3), which, because it is a weak acid, remains largely in the undissociated form, releasing far fewer H+ ions into the solution than the original strong acid would have done.The pH of a buffer solution depends solely on the "ratio" of the molar concentrations of the weak acid to the weak base.