Throughout the series of SparkNotes on acidsbases, we have focused on calculating the pH of solutions. Now, we'll take a look at a more practical side of acid-base chemistry--how to measure the pH of a solution. The experiment that measures the pH of a solution is called a titration. Titrations involve the addition of a known amount of an acid or base to neutralize an unknown amount of acid or base. From the amount of acid needed to neutralize the base, or base to neutralize the acid, one can calculate the pH of the original solution. To detect the endpoint of a titration, an indicator is used. An indicator is an acid or base whose conjugate acid or conjugate base has a different color from that of the initial form. As the pH of the solution comes to equal the pKa of the indicator, a sharp color change is observed. We will examine how the shift of the indicator to its conjugate form is related to the Henderson-Hasselbalch equation.
An interesting property of titration is the titration curve--a plot of solution pH versus titrant volume. We can extract useful information from the titration curve of a solution. In this SparkNote, we will study the different types of titration curves and discuss the chemistry behind them.