Titration and p H Measurement

Abstract Titration is the quantitative addition of a solution of known concentration to a solution of unknown concentration until the reaction between them is complete to determine the concentration of the second solution. An acid–base titration is the quantitative determination of the concentration of an acid or a base. Titration of an acid with a base requires that the pH, or relative concentrations of the two reactants, be monitored. pH can be assessed by litmus paper or by indicators, for example, phenolphthalein, but these methods lack precision. Typically, pH measurement in the laboratory is done by measuring the cell potential of that sample in reference to a standard hydrogen electrode. A plot of the pH of an acidic (or basic) solution as a function of the amount of added base (or acid) is a titration curve. From this, the endpoint or equivalent points can be determined. Key Concepts: Acid–base titrations determine the concentration of an acidic (or basic) solution (the analyte) by the delivery of a measured volume of base (or acid) of known concentration (the titrant). The progress of an acid–base titration is often monitored by a titration curve.