Lab Name: Molar Mass by Freezing Point Depression
Researcher: Isabella Cuenco
Lab Start Date: November 9, 2012
Lab Completion Date: November 9, 2012
Table of Contents
The purpose of the lab is to find the molar mass of an unknown substance by measuring the freezing point depression of a solution of the unknown substance and BHT.
Hypothesis: If the freezing point depression of a solution of an unknown substance and BHT is measured, the molar mass of an unknown substance can be found.
a. Determine the freezing point depression
53.02 – 50.78 = 2.24 °C
b. Calculate the molar mass of the unknown substance
7.1 °C/m X 2.04 g (solute) X 24.8 g (solvent) X 2.24 °C = 260.0 g molar mass = 260. g
2. What are colligative properties?
Colligative properties are properties of a solution that change when the condition of the solution changes.
Set up a Bunsen Burner, ring stand and clamp, as shown in picture below.
Fill a beaker with 100 mL of water
Place beaker on ring stand, and light burner to test that blue of flame is hitting the bottom of the beaker; once it is, turn burner off. 4.
Using a mortar and pestle, crush 0.5 g of BHT.
Pack the BHT into a small capillary tube.
Using a rubber band, fasten the capillary tube to a thermometer, ensuring the bottom of the tube lines up with the thermometer bottom.
Clamp the thermometer/tube, ensuring the thermometer and tube are in the water. 8.
Begin to heat the water and observe the tube.
Once the BHT has melted (turned from white powder to clear), turn off the heat, and record the temperature at which the BHT melted. 10.
Once cool, dispose of the BHT and tube.
Using a mortar and pestle, crush 0.1 g of cetyl alcohol. 12....
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