Science, Tech, Math › Science Titration Basics Determine the Molarity of an Acid or Base Share Flipboard Email Print Hill Street Studios/Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 07, 2019 Titration is a procedure used in chemistry in order to determine the molarity of an acid or a base. A chemical reaction is set up between a known volume of a solution of unknown concentration and a known volume of a solution with a known concentration. The relative acidity (basicity) of an aqueous solution can be determined using the relative acid (base) equivalents. An acid equivalent is equal to one mole of H+ or H3O+ ions. Similarly, a base equivalent is equal to one mole of OH- ions. Keep in mind, some acids and bases are polyprotic, meaning each mole of the acid or base is capable of releasing more than one acid or base equivalent. When the solution of known concentration and the solution of unknown concentration are reacted to the point where the number of acid equivalents equals the number of base equivalents (or vice versa), the equivalence point is reached. The equivalence point of a strong acid or a strong base will occur at pH 7. For weak acids and bases, the equivalence point need not occur at pH 7. There will be several equivalence points for polyprotic acids and bases. How to Estimate the Equivalence Point There are two common methods of estimating the equivalence point: Use a pH meter. For this method, a graph is made plotting the pH of the solution as a function of the volume of added titrant.Use an indicator. This method relies on observing a color change in the solution. Indicators are weak organic acids or bases that are different colors in their dissociated and undissociated states. Because they are used in low concentrations, indicators do not appreciably alter the equivalence point of a titration. The point at which the indicator changes color is called the end point. For a properly performed titration, the volume difference between the endpoint and the equivalence point is small. Sometimes the volume difference (error) is ignored; in other cases, a correction factor may be applied. The volume added to achieve the end point may be calculated using this formula: VANA = VBNB where V is volume, N is normality, A is acid, and B is a base.