The purpose of this lab is to determine the molecular weight of a compound by measuring the freezing point depression. This is done by measuring the freezing point of a pure solvent, lauric acid. The freezing point of a mixture of lauric acid and an unknown solute is measured. From the freezing point change obtained, the formula weight of the solute can be calculated. To obtain the cooling curve, the melted solvent or the melted solution must be cooled very slowly. During this time, the temperature of the system is monitored and the contents of the test tube are continuously mixed. The expected results are determined by the cooling curve, and using the formula:
These results are important because if the formula weight is calculated wrong then the unknown compound found will be wrong.