CHEM 213 George Mason University Molecular Mass by Freezing Point Depression Lab Report
In this experiment we determined the molecular mass of
isopropyl alcohol (rubbing alcohol) by measuring the freezing point of an aqueous solution of the
alcohol.
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Distilled Water
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Distilled Water + Isopropyl Alcohol |
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Trial One |
Trial Two |
Trial One |
Trial Two |
|
Volume of Distilled Water (mL) |
15 mL |
NOT PROVIDED |
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Mass of Distilled Water (kg) |
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Volume of Isopropyl Alcohol (g) |
NOT PROVIDED |
4 mL |
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Mass of Isopropyl Alcohol (g) |
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|
Time (sec) |
Temperature (ºC) |
Temperature (ºC) |
Temperature (ºC) |
Temperature (ºC) |
|
0 |
15.9 |
22.1 |
20.7 |
21.6 |
|
30 |
13.1 |
19.9 |
12.1 |
12.5 |
|
60 |
10.5 |
17.0 |
8.0 |
8.2 |
|
90 |
8.6 |
14.9 |
4.9 |
4.3 |
|
120 |
7.5 |
12.2 |
1.6 |
2.4 |
|
150 |
6.5 |
9.9 |
-0.5 |
0.3 |
|
180 |
5.0 |
7.4 |
-2.6 |
-0.6 |
|
210 |
3.7 |
5.0 |
-4.4 |
-2.6 |
|
240 |
2.4 |
3.1 |
-4.7 |
-3.7 |
|
270 |
1.2 |
1.0 |
-6.1 |
-4.0 |
|
300 |
0.1 |
0.9 |
-6.6 |
-5.6 |
|
330 |
-0.3 |
1.1 |
-5.2 |
-5.1 |
|
360 |
0.5 |
1.4 |
-4.9 |
-4.7 |
|
390 |
0.6 |
1.3 |
-5.5 |
-5.2 |
|
420 |
0.9 |
0.7 |
-5.5 |
-5.1 |
|
450 |
0.7 |
0.9 |
-5.8 |
-5.7 |
|
480 |
1.0 |
0.6 |
-6.2 |
-5.4 |
|
510 |
0.8 |
0.7 |
-5.9 |
-4.9 |
|
540 |
1.0 |
0.7 |
-5.9 |
-4.5 |
|
570 |
1.0 |
0.4 |
-6.2 |
-5.1 |
|
600 |
0.5 |
-6.0 |
-5.1 |
|
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Freezing Point (ºC) |
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Average Freezing Point (ºC) |
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ΔTf(°C)
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Mexp’t (moles/kg)
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Moles of Isopropyl Alcohol (moles) |
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Molecular weight of Isopropyl Alcohol (g/mol) |
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% Error of Molecular Weight of Isopropyl Alcohol |
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– Find all of the information missing in the Data table and show your work.
– Make an Excel worksheet “Results” showing the calculated results – each in a separate row. Make sure to show an example calculation for each column on the bottom left. The columns should include:
m_H2O = Mass of distilled water solvent
m_Iso = Mass of Isopropyl alcohol
dt_f = Freezing point depression
m_expt = Molality
Mol (Isopropyl) = Moles of isopropyl alcohol in mixture
MW (Isopropyl) = Molecular mass of isopropyl alcohol
% Error = Percent error
– Create an Excel chart ‘Freezing Point Determination’ with the variables time on the x-axis and
temperature on the y-axis to determine the freezing point. An example of how the chart should look like in attached below. My excel is really old so please include a picture of the graph in your submission as well as in excel.
– Answer these discussion questions:
Define the freezing point of a solution?
What may be a reason why an alcohol/water mixture does not freeze at a constant
temperature?
What are the possible sources of error in this experiment?
Please let me know if you have any questions or if you think i missed any information you might need.
