Analysis of a Volatile Liquid

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Analysis of a Volatile Liquid

The purpose of this experiment was to use various methods of analysis to determine the identity of an unknown volatile liquid. In the first part of the experiment, the molecular mass was found by using water to find the volume of a flask through calculations and this as well as the mass of the gas of the unknown liquid were put into the a manipulated version of the ideal gas equation to determine the molar mass of the liquid, which was 14.21g per mole. The next part was used to determine the density of the volatile liquid. First the volatile liquid was placed in a pyncometer and massed; water was then placed in the same (now clean and empty) pyncometer and massed. The density equation was manipulated using the data for water to solve for the mL of the capillary tube. This new information was used to find the density of the liquid, which was 1.33g/mL. The last part of the experiment was used to determine the boiling point of the volatile liquid. A test tube was placed inverted in a flask filled with the unknown liquid that was in a water bath heating. When bubbles from the test tube slowed and began to go back into the test tube, the temperature was taken and this served as a measurement of the boiling point. The average measured boiling point was 60.2°C. The measured data was inadequate to identify the liquid with. The unknown liquid was revealed to be methanol; the revealed identity could then be used to compare the data to the actual information for methanol. The molar mass was found to have a percent error of 55.6%, the density had a percent error of 68.1% and the boiling point had one of 6.95%. The measured data for the boiling point was fairly accurate, but the molar mass and the density both had very large percent error. The reasons for this will be discussed more in the discussion.


Boiling Point
Trial| Boiling Point (Degrees Celsius)|
1| 63.2|
2| 59.3|
3| 58.1|

Molar Mass
Trial| Mass of Flask and Gas (g)|
1| 29.118|
2| 29.120|
3| 29.129|
Item| Mass (g)|
Flask (used for trials)| 29.111|
Flask (used with water)| 28.81|
Flask filled with water| 60.99|
Water| 32.18|

Item| Mass (g)|
Pyncometer| .058|
Pyncometer with volatile liquid| .078|
Pyncometer with water| .073|
Volatile liquid| .020|
Water | .015|

Miscellaneous Data
Item of Data| Value|
Room Temperature | 25°C|
Pressure of Room| .960atm|


Boiling Point

Average Boiling Point: (63.2+59.3+58.1)/3= 60.2° C
The average boiling point was found by adding each boiling point measured in each of the three trials and dividing this value by three.

Percent Error: {(64.7-60.2)/64.7} x100=6.95%
The percent error was found by subtracting the actual value from the theoretical and then dividing this value by the theoretical. This value is then multiplied by 100 to find a percent.

Molar Mass

Volume of the flask: 32.18g/0.9975g/mL=32.26mL
The density of water at room temperature was found to be .9975g/mL. The density equation was manipulated so that the volume of the container could be found by dividing the grams of water in the flask by the density of water. This was then converted to liters by dividing the amount of mL by 100 because there are 1000 mL in a liter.

Mass of gas: 29.129-29.111=.018g
To find the mass of the gas, the mass of the flask was subtracted from the mass of the flask with gas in it.

Molar mass of the volatile liquid: {.018g x 0.0821 x 298K}/(.960atm x .03226L)=14.21g To find the molar mass the ideal gas equation is manipulated to find the molar mass. The equation was MM=gRT/PV. The grams of the gas was multiplied by the R constant and the temperature of the room. Then, this value was divided by the pressure of the room multiplied by the volume of the container.

Percent Error: {(32.04-14.21)/32.04}x100=55.6%
The percent error was...
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