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Chemistry Laboratory I (CHM 113) Lauric Acid Freezing Point

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University of Miami

Chemistry Laboratory I (CHM 113)

Rachel Tammone
CHM113 Section 7R Heather Pedziwiatr
4/5/14
Freezing Point Depression: Lauric Acid
Purpose: The purpose of this lab is to determine the freezing point depression constant (Kf) for
lauric acid by using Lab Pro. Kf can be considered because Lauric acid is a non-electrolyte. It is
important to learn about freezing points because in the process of freezing, impurities interfere
with normal molecular interactions. Impurities lower the temperature needed for a solid to
solidify. This becomes useful to understand and know in regions of the world where snow is
predominant. Putting salt down on the roads prevents icing by lowering the freezing point of
water.
Theory: In order to perform this experiment successfully, pure lauric acid, .75g BA/ 8g LA, and
1.50g BA/ 8g LA will be monitored with a temperature probe in order to determine the freezing
point depression constant. The samples must be heated until they are fully liquefied and then
placed in a beaker of cold water so they solidify. As the samples solidify the temperate probe
will keep track of the temperature, so the freezing point and change in temperature can be found.
The formula ΔT=Kf m is used to find the freezing point depression constant after figuring out the
change in temperature and the molality of the samples Molality equals the moles of solute
divided by the mass of the solvent. Averaging the freezing point depression constant from the
two impure samples allows one to find the average Kf of lauric acid.
Procedure:
1. Attach the temperature probe to CH1 on the Lab Pro interface, & connect the interface to
the computer. Start the Logger Pro software & open the appropriate files so the title of
the graph reads “freezing point of lauric acid”
2. Place a 400 mL beaker filled with water on a hotplate, but do not turn the hotplate up past
three.
3. Obtain a test-tube containing pure lauric acid and place it in the beaker so it melts. When
it is fully melted, remove it from the water bath.
4. Put the temperature probe into the test tube and being stirring the molten lauric acid. Wait
5 seconds then hit collect on the Lab Pro screen on the computer.
5. Place the test tube with the temperature probe in it in a beaker filled with cold/room
temperature water.

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Chemistry Laboratory I (CHM 113) Lauric Acid Freezing Point

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