The purpose of the lab is to determine the molecular weight of a compound by measuring the freezing point depression. We determined this by experimenting with lauric acid to obtain the freezing point depression of the solution. We calculated the formula weight of the solute (unknown 2) using the freezing point constant (3.90K kg mol-1), the mass of the solute (0.51g), the freezing point depression (2°K) obtained from the experiment, and the mass of the solvent (0.00806kg). We concluded that the formula weight of the unknown sample was 123.4 g/mol for the first trial and 122.9 g/mol for the second trial. By looking at table 2 and the formula weights of different compounds we were able to determine the identity of the unknown, which was Benzoic Acid. The formula weight of Benzoic Acid is 122.4, which is the closest to our results.
Some sources of error that may have occurred in the experiment include, not heating the solution properly so that all the crystals of the unknown substance dissolved properly. Another error may have occurred when transferring the lauric acid or unknown substance into the test tube and some of the substance may have been stuck on the weighing dish or may have landed on the working station, thus altering the results. Another source of error may have occurred due to the rate of stirring. Some of the contents may have been lost when the copper coil was been moved up and down too fast.