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Baton Rouge Community College
Experiment title:
Experiment 8 - Molecular Weight of Unknown Compound
Course/Section #:
Chemistry 1121
Semester:
Spring 2024
ABSTRACT:
The purpose of this experiment is to measure the molar mass of unknown volatile liquid and identity it. The reaction was carried out by following method: https://www.youtube.com/watch?v=YXQocxXmt-E The equation used in this experiment are: Density = mass / volume MW = dRT /P Where MW = Molecular weight P = Pressure of the room in atm
d = Density, grams of liquid divided by volume of container T = Temperature of boiling water in kelvin R = Universal gas constant
Chemicals:
Name Chemical Formula Hazard Acetone CH 3 COCH 3 N/A
DATA/ANALYSIS:
Procedure
- Placed the flask on weighing balance and measured the mass of flask.
- Added 5 mL of volatile liquid in flask.
- Covered the flask with foil and poked a hole in it.
- Boiled the water in beaker, observed the temperature and placed the flask in it.
- Once all liquid is vaporized, removed the flask and allowed the gas to condense.
- Measured the weight of flask.
- Repeated the procedure one more time.
DATA TABLE
R= 0.08206 L atm / mol K Trial 1 Trial 2 Initial mass of flask 126.07 44 g 126.0744 g Volume of flask 0.280 L 0.280 L Pressure 0.9966 atm 0.9966 atm Temperature of boiling water 367 K 369.5 K Mass of flask after condensation 126.5011 g 126.5902 g
MW = 56.05 g / mol
Taking average of both MW = (46.36 + 56.05) ½
Molecular weight of the unknown = 51.20 g / mol
Possible compounds:
Acetone = 58.09 g/ mol
Cyclohexane = 84.18 g/ mol
Ethyl acetate = 88.12 g /mol
Apparatus:
CONCLUSION:
In this experiment, we learned how to determine the molecular weight of an unknown volatile liquid. We correctly determined the molecular weight of the unknown liquid, and based on our possible compounds, we can conclude that it is acetone. The 11.86% inaccuracy could be due to vapors escaping from the hole in the foil. It could be due to incomplete condensation, gas, or some other human mistake. It can be improved by implementing specific procedures. Nonetheless, we successfully identified the unknown compound.
