Name _____________________________
Period __________ March 5, 2014
Fractional Distillation
ChemCom Lab A.5 pg. 277
Substances can be separated by taking advantage
of their different physical properties. In the
petroleum industry, engineers use differences in
the boiling points to separate crude oil into
separate, useful fractions. The process is called
fractional distillation. In a refinery this process
takes place in large, vertical, distillation towers.
In this experiment the goal will be to use a
simplified fractional distillation set up to separate
and identify two liquids that are mixed together.
The mixture contains two of the liquids found in
Table 3.2 below. Two properties will be used to
identify the liquids; boiling points and the
reaction of each pure liquid with iodine (a nonpolar solid).
Figure 1
MATERIALS:
Logger Pro
Temperature Probe
Condenser with two hoses
Small Bunsen burner
Unknown mixture of liquids
Bent-glass tubing
3 small beakers (labeled: 1, X, 2)
250-mL or 500-mL flask
3 ring stands
3 utility clamps
3-4 boiling chips
2-hole stopper
COMPUTER SET UP:
- Be sure temperature probe is plugged in and connected to the Vernier interface.
- Open ‘Fractional Distillation’ Logger pro found in your teacher’s OUTBOX.
PROCEDURE:
Day 1 – Fractional Distillation
Assemble a distillation system (Figure 1).
Have it checked by your teacher.
Replace the hot plate with a small Bunsen burner.
Add about 50 mL of the mixture and a few boiling
chips to the round flask.
Turn on the cooling water.
(Don’t melt the Temperature Probe wire!)
Beaker #1:
Click Collect to begin data collection and begin to heat the liquid with a medium flame.
The temperature should rise sharply and then stabilize for a while at the boiling point of the first fraction.
Collect a few milliliters of the first liquid to condense/drip out of the column in a small beaker.
This first liquid is called ‘Fraction 1’. Label the beaker #1 and set it aside for iodine testing.
Beaker X:
Put a new beaker under the cooling column (beaker labeled ‘X’). The temperature will begin to rise faster
again while a mixture of the two fractions boil. The material collected in this second beaker (labeled ‘X’) is not
pure and will not be used. It is a mixture of the two liquids. When the temperature starts to stabilize for the
second time switch the beakers again. Put the beaker labeled ‘X’ aside.
Beaker #2:
The third beaker (labeled #2) will be used to collect the second liquid in the mixture, ‘Fraction 2’.
Fraction 2 should be the last liquid to boil. (STOP HEATING BEFORE ALL OF THE LIQUID IS GONE!)
After you have collected a few mL of Fraction 2, click Stop to end data collection.
Turn off the gas to the Bunsen burner. Beaker #2 should be set aside for I2 testing.
Cover the #1 and #2 fractions with parafilm and store them in the designated area.
ANALYZE AND PRINT YOUR DATA
- Print copies of the graph for each person in your group (FILE, PRINT, GRAPH).
- Draw horizontal lines across your graph showing the boiling temperatures of fractions 1 and 2. (plateaus)
- When you determine the boiling temperatures for each fraction, label the values on your printed graph.
DAY 2 – Testing the fractions with I2:
Test fractions 1 and 2 with I2 by mixing a few crystals of I2 with each liquid. Swirl to try to dissolve the iodine.
Record the final color of the fractions with the iodine mixed in them. ALSO, determine which liquid dissolves
the I2 better.
QUESTIONS
1. What were the boiling points of
Fraction 1: ____________oC
Fraction 2:____________oC
2. When I2 was added, what color did each fraction become?
Fraction 1: ____________
Fraction 2:____________
3. Based on the data collected, identify each fraction as one of the liquids listed in Table 3.2 below.
(Support your claim with evidence.)
Fraction 1: ___________________ Fraction 2: ___________________
4. Which of the two substances in Table 3.2 below would be most difficult to separate by distillation? Why?
Temperature
5. Sketch a graph of temp vs. time showing what a fractional distillation graph of a mixture of all four
substances listed in Table 3.2 below.
Temp vs. Time
Time
5. If this sample were mixed with crude oil and distilled in a tower, based on the boiling points of fraction #1
and #2, which fraction would be collected lower in the tower? Which fraction would be collected closer to the
top of the tower? (see figure 3.14 below)
Figure 3.14