Introduction/Background:

By determining the stoichiometric ratio of a balanced equation, one can predict the amount of one reactant or product when another is known. Such a prediction can be made by using the formula: c = n/V. In this equation, "c" represents the concentration of the substance (mol/L), "V" represents the volume of the solution (L), and "n" represents the amount of substance (mol). This simple process is commonly known as titration. During a titration, an indicator produces a visual signal when one reactant has been completely used up (when the equivalence point has been reached). At this point, the number of moles of the other reactant can be determined by using the volume, molarity, and stoichiometric ratio. During this lab, this technique is used to standardize a solution of sodium hydroxide, and thus accurately determine the molarity of the solution. Although indicators are used in this lab, in order to avoid subjectivity, a pH sensor will be used to detect the equivalence point. The sensor monitors the pH as the titrant solution is added, and thus the steepest point of the curve represents the equivalence point.

Purpose:

To determine the concentration of a sodium hydroxide solution by titrating it with a standard solution of known concentration.