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Organic chemistry pre-lab questions

1. Why is it dangerous to heat a liquid in a distilling apparatus that is closed tightly at every joint and has no vent to the atmosphere?

2. In your distillation of the binary mixture, which fractions contained more of the
higher boiling component, the earlier fractions or the later fractions?

expriment procedure

Use a modification of the apparatus used previously to distill a mixture of 25 mL of
hexane and 25 mL of toluene. Use a 100-mL round-bottom flask. Remember to add a fresh
boiling stone. Label three sample vials (from the side shelf) as â??Fraction 2â??, â??Fraction 5â?? and
â??Last Fractionâ??. Heat the reaction flask in the sand bath on low heat (less than 50%, not literally
â??lowâ?? setting on your hot plate) and distill the volatile product into a graduated cylinder. Wrap
the heated portion of your distillation apparatus with aluminum foil above the liquid level in the
flask all the way up to the thermometer bulb. In order to obtain differences in fractions resulting
from differences in boiling points, it is important not to distill the products too quickly. This will
be reflected in your technique grade for this experiment.
Record the temperature in your notebook after every 1-2 mL as the distillation proceeds. Use the
graph as shown below as an example. Collect and save the second, fifth, and
last fractions in vials (on the side shelf) for use in the experiment on gas-liquid chromatography.
Keep distilling until you have collected 16 mL of distillate. Discard the other fractions in the
Liquid Organic Waste container in the hood.

3.. Does a pure liquid in a distilling flask vaporize all at once when the boiling point is reached?

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Solution Preview

1) Since vapor expands as it heats, if you do not vent the gas, your apparatus could explode.

2) The later fraction ...

Solution Summary

In this solution we consider 3 questions relating to organic chemistry lab, specifically the setup and use of distillation glassware. The answers are succinct and to the point.