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Lewis Lab Structure

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Submitted By maureenshultz
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Experiment #8
Molecular Weight by freezing Point Depression
Maureen Shultz
November 14, 2015

I. Purpose
The purpose of this experiment was to determine the molecular weight of two unknown substances by measuring the freezing point depression of an aqueous solution of the unknown substances.

II. Experiment Method

Equipment: Test tube Constant temperature bath Thermometer

Chemicals: H2O Unknown substance #1 Unknown substance #2

To begin this experiment, I started by placing an empty test tube on the solid surface workstation and poured 10mL of H2O into the test tube. I then attached a thermometer to the test tube, documenting that the liquid is clear in color. I then placed a constant temperature bath onto the solid surface workstation. I set the temperature of the constant temperature bath to the freezing point of ethylene glycol ,-15 degrees Celsius. When the desired temperature is reached, I gently place the test tube into in the constant temperature bath. Carefully observing the test tube, I noticed an ice formation, and then documented the temperature at which the freezing point of the solution became a solid. I then carefully clear the workstation and set up for the next experiment.

A second empty test tube is placed on the solid surface workstation. I then pour 2 grams of the first unknown sample substance into the empty test tube and attach a thermometer. I notice a silver substance in the bottom of the test tube. I add 10mL of water into the test tube and note that the liquid in the test tube is clear in color without any reaction. I then place the constant temperature bath on my solid surface workstation and turn the temperature setting to the freezing point of ethylene glycol at -15 degrees Celsius. Once the desired temperature is reached, I carefully place my test tube with the unknown first substance and water in

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