CHE 231 - Distillation

The X-axis of the phase diagram

Mole fraction of hexane

The y-axis of the phase diagram

Temperature

In this experiment, how many fractions will be collected during the first distillation?

3

What is the boiling point of hexane in units of degrees C?

69 degrees C

What is the boiling point of toluene in units of degrees C?

111 degrees C

In this experiment, how would you determine the composition of the fractions collected?

Gas chromatography

What is the stationary phase in gas chromatography (GC)?

A high boiling liquid supported on an inert solid support

What is the mobile phase of gas chromatography?

Helium

Which one would elute first on a GC, hexane or toluene? Why?

Hexane elutes first because it has a lower boiling point

At the end of the experiment, where will the separated fractions be disposed?

Organic liquid hazardous chemical waste container

True or False: Boiling point and vapor pressure are directly proportional

False

True or False: The first fraction in your distillation experiment will be mostly composed of toluene

False (hexane)

True or False: The greater the number of theoretical plates better the separation. Fractional distillation columns are capable of separating substances because they contain large surface areas that allow for multiple simple distillations and, thus, many theoretical plates.

True

What is distillation?

Distillation is the process of separating individual liquids from each other either by heating or cooling the mixture. The separation is based upon the differences in their boiling points (and thus the vapor pressure).

How is fractional distillation achieved in this experiment?

Fractional distillation is achieved in this experiment by heating up a mixture that contained liquids with different boiling points twice - this experiment had two theoretical plates which is how fractional distillation was achieved. The two theoretical plates were the first distillation and the second distillation. As the mixture boiled the evaporated liquid of an individual liquid was condensed back into a liquid which was collected. Since the liquids had varying boiling points, the individual components could be separated this way.

What is the purpose of performing the second distillation/re-distillation?

The purpose of performing the second distillation was to remove any impurities from that fractional collection. Since the fraction chosen was to have a greater amount, it is likely that part of the sample was not the liquid that was meant to be collected during that range of heating.

Determine if the following pair(s) of compounds could be effectively separated by simple distillation?

Has to have a difference in boiling point difference of preferably between 30-40 degrees C

On which physical or chemical property does the GC separate the compounds?

ANSWER

What is the formula to calculate % composition of hexane?

% composition of hexane = [(Area of Hexane)/(Area of Hexane + Area of Toluene)] x 100

What waste container do gloves go in?

Regular trash

What waste container do pipettes go in?

Broken Glass Waste

What waste container do boiling chip go in?

Solid hazardous chemical waste

What waste container do acetone go in?

Organic Liquid Hazardous chemical waste

What waste container does hexane go in?

Organic Liquid Hazardous Chemical waste

What waste container does toluene go in?

Organic Liquid Hazardous Chemical Waste

Why is it called fractional distillation?

Since two rounds of distillation occur, the process has two theoretical plates and is therefore called fractional distillation.

What is the Hickman column?

A short column, so a complete separation of hexane and toluene cannot be achieved in one cycle.