Freezing Point Depression Lab

The goal of this experiment is to find the molar mass of an unknown substance by measuring the freezing point depression of a known amount in an aqueous solution. Freezing point depression is a colligative property of solutions. There are three other properties, which are boiling point elevation, vapor pressure depression, and osmotic pressure. Colligative properties of a solution depend on the amount of solute and solvent molecules and not the specific properties of the molecules. The temperature at which the solvent starts to freeze will be specified as the freezing point of the solution. The freezing point temperature will be found by cooling down the substance in a bath filled ice and salt mixture past its freezing point. Mixing salt and ice decreases the freezing temperature of water, lowering the freezing point of the new mixture. This makes the freezing point lower than temperature attainable with only ice as a pure solvent. The temperature is plotted as a function of time and the cooling curve is constructed. With the freezing point, the molar mass of the solute can be determined. It is hypothesized that by finding the freezing point the molar mass of the substance will accurately be determined.

Methods: The experiment was produced
The solvent used is water, which means the unknown substance is dissolved in water. The freezing point of water is measured by cooling a sample of water and recording the temperature as a function of time. The resulting data are used to create a cooling curve, shown in Figure 1. The data were plotted using Microsoft Excel. This was also to determine if the thermometer was calibrated correctly. It is known that the freezing point of water is 0℃; if the cooling curve does not correspond with this previous knowledge it will be known that the thermometer reading is off and will be taken into account when determining the molar mass of the