Lab: Importance Of Fractional Distillation

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Pages: 4
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Danielle Tiska
Experiment 4: Fractional Distillation
Chemistry II Lab 2125-10
February 20, 2017

Abstract:
The main goal of this lab was to better understand fractional distillation and its importance. The importance of fractional distillation is a separating technique that uses boiling points of individual components to separate compounds. The secondary objective was using fractional distillation to identify the parts of an unknown. The fractional distillation apparatus was used, to find the low boiling point of unknown #5, which was 65C, and the high boiling point ,which was 96C. Those two boiling points led to the conclusion that unknown 5 was composed of methanol and 1-propanol.
Introduction:
Fractional distillation is used when separating …show more content…
Then, the three-way adapter was connected to the fractioning column. After, the west condenser was attached to the three-way adapter using a keck clamp. A 15 mL centrifuge tube was attached to another smaller ring stand and placed directly under the west condenser. To complete the set-up, the thermometer adaptor was placed on the top of the three-way adapter and the thermometer was placed just so the tip of the thermometer was right below the side arm of the adapter.
The heating mantle was plugged in and turned on. The voltage was placed at 50 volts. After a period of time the liquid began to drip into the centrifuge tube. The temperature was recorded every .5 mL until 4 mL was collected, and then the centrifuge tube was changed and the voltage was increased to 75 volts. The steps were repeated with the next tube, but this time the centrifuge tube was not changed until 5 mL. The centrifuge was changed one more time and the steps were the same as before and the last tube was removed at 4mL. Then the apparatus was shut off.
The refractive index was found from the first and third tubes. A drop of the first fraction was taken with a plastic pipette and placed on the refractometer. The colors were aligned and the index was recorded. This was then repeated for the third …show more content…
The temperatures recorded from the experiment caused the graph to have two distinct plateaus. One of the plateaus were seen at 65C and constantly stayed around that range for about 6 mL. This plateau shows that the first part of the mixture, had a boiling point of about 65C. When that number was compared to the table of knowns, the low boiling point was closely related to methanol, which had a boiling point of 64.7C. Not only were the boiling points close, the refractive index of the first fraction was 1.3276, while methanol’s refractive index is 1.3292 which is rather close. After the first plateau, the temperature rose for about 3mL as the heating mantle was increased. The second plateau started at 96C and stayed that way for the whole third fraction. The constant in temperature showed that the high boiling point was met. The high boiling point value was a close match to 1-propanol which had a boiling point value of 97.2C. This small change could have resulted in the misplacement of the thermometer. 1.3840 was the refractive index found for the third fraction, which is exactly the same as the known refractive index of 1-propanol. The observed boiling points and the observed refractive index concludes that unknown 5 is composed of both methanol and
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