We will investigate these curves by following a particular example in detail. Let us calculate the pH values along the course of a particular titration, the titration of exactly 100 mL of 0.100 molar acetic acid with 0.100 molar sodium hydroxide. In practice, we would probably titrate 25.00 mL instead for convenience, but these volumes are selected to simplify some of the calculations. In the course of the calculations and discussion, we will answer such questions as the titrant to use, the indicator to select, and what manner of solution is present at various points along the titration curve. First, consider the titrant solution.
Acetic acid is a weak acid, so a base is required to obtain any acid-base reaction.
To get a pH break which is as large as possible at the equivalence point we should choose a strong base. The common strong bases are NaOH and KOH, so we choose one of these. It is normal to choose a concentration of base that will give us a reasonable volume to add, so that the volume can be accurately measured and yet not be too large. The pH slowly rises as the NaOH added reacts with the acetic acid. The acetic acid has been one-quarter titrated when 25 mL of the NaOH solution have been added.