The purpose of this lab is to learn how to determine the molecular weight of a compound by measuring the freezing point depression. Measuring the freezing point of a pure solvent, lauric acid, does this. In the lab we will first melt and then freeze the lauric acid in a test tube with a copper wire for stirring. The contents of the test tube will be melted using a water bath on a hot plate. The temperature will be recorded with a sensor and graphed versus time. This same procedure will be performed a second time after the unknown metal is added to the lauric acid. The added solute creates a decrease in the freezing point. From this change in the freezing point depression, the formula weight of the solute can be calculated using the equation:
The calculated formula weight will then be compared with those given in the lab handout to determine the identity of the unknown solute. These results are important because if the formula weight is calculated wrong then the unknown solute identity will be incorrect.