CHEM 241 UNLV Microscale Distillation And Gas Chromatography Lab Report Please use the data and experiment video provided and follow all directions as well

CHEM 241 UNLV Microscale Distillation And Gas Chromatography Lab Report Please use the data and experiment video provided and follow all directions as well as use the uploaded template to record all the information. Use the data provided for the answers. I have attached the manual information, lab report format, as well as fractions 1 and 2. Thank you. Experiment #1-1:
Microscale Distillation (Hickman Still distillation)
Distillation is a common technique used to separate and purify a liquid component from a mixture
based on differences in boiling points of the liquids. Simply stated, distillation involves heating a
liquid mixture to its boiling point, where liquid is rapidly converted to vapor. The vapors, richer in
the more volatile component, are then condensed into a separate container. When the
components in the mixture have sufficiently different vapor pressures (boiling points), they can be
separated by distillation.
The purpose of this experiment is to illustrate the use of distillation for separating a mixture of two
volatile liquids with different boiling points, hexane (69 °C) and toluene (110.6 °C). Hickman Still
distillation will be used to separate the mixture of hexane and toluene, and the result will be
compared by analyzing the composition of the distillate (the distilled liquid) using Gas
Chromatography (GC). You will also construct a graph of the distillation temperature vs. time. This
graph will allow you to determine the approximate boiling points of the two liquids.
Experiment #1-2: Gas Chromatography
INTRODUCTION
Gas chromatography is one of the most useful instrumental tools for separating and analyzing
organic compounds that can be vaporized without decomposition. Common uses include testing
the purity of a substance and separating the components of a mixture. The relative amounts of
the components in a mixture may also be determined.
THE PRINCIPLE OF GAS CHROMATOGRAPHY
Gas chromatography separates the components of a mixture primarily on the basis of their vapor
pressures (or boiling points). A sample is injected into the heated injection port, and it is
immediately vaporized and introduced into a moving stream of gas, called carrier gas (mobile
phase). The vaporized sample is then swept into a capillary column (a long and a narrow tube
with the stationary phase coating the interior surface), which is contained in a temperaturecontrolled oven. As the sample passes through the column, it is subjected to interact with the
phase coating (non-polar phase column will be used in this experiment), and the components are
separated. As each component leaves the column at different times (retention time), its presence
is detected by a detector (flame ionization detector) that generates a signal that is recorded as a
chromatogram (refer the Figure 1).
Figure 1. Schematic diagram of a gas chromatograph
Several factors determine the rate at which a given compound travels through a gas
chromatograph as below.
a. Compounds with lower boiling points will generally travel through the gas
chromatograph faster than compounds of higher boiling points.
b. The rate of flow of the carrier gas.
c. Choice of liquid phase used in the column.
d. The length of the column.
QUANTITATIVE ANALYSIS
The area under a gas-chromatograph peak is proportional to the amount (moles) of compound
eluted. Hence, the molar percentage composition of a mixture can be approximated by comparing
relative peak areas. The simplest method of measuring the area of a peak is by geometrical
approximation, or triangulation. In this method, you multiply the height h of the peak above the
baseline of the chromatogram by the width of the peak at half of its height w1/2 (illustrated in Figure
2). The base line is approximated by drawing a line between the two side arms of the peak. To
obtain a percentage composition for the mixture, first add all the peak areas. Then, to calculate
the percentage of any component in the mixture, divide its individual area by the total area and
multiply the result by 100.
Figure 2. Triangulation of a peak.
In this experiment, the “Fraction #1 & #2” will be used as your samples, and they will be analyzed
quantitatively by triangulation method. Then, the efficiency of the Hickman Still distillation will be
evaluated based on the gas-chromatograph result. Your instructor will inject your samples for your
group.
PROCEDURE (experiment video, https://youtu.be/SVR8GudqBEI)
1. Place one boiling chip in a 5 mL conical vial.
2. Using a graduated cylinder, add 2 mL of hexane and 2 mL of toluene to the 5 mL conical
vial.
3. Assemble the apparatus as shown in demo by your instructor. Make sure that the side
arm of your Hickman Still has a cap with a septum.
NOTE: Carefully insert the thermometer into the Hickman Still head, having the bulb of the
thermometer rest on top of the glass spikes.
4. Make sure the apparatus is vertical and straight. Have your instructor check your setup
before you begin distillation.
5. Turn on the hot plate by setting the heat to about “2” (old hot plate) or “130” (digital hotplate)
and adjust the stirrer speed to the optimum position.
6. Continuously collect all distillates into a 3 mL conical vial up to 60 – 70 °C, and label this
vial as “Fraction #1”. Close the 3 mL conical vial with a septum and a cap, and then seal
it with a small piece of parafilm.
NOTE: The rate of condensation in the Hickman Still should be slowed down over time.
7. Continue to heat the mixture until the temperature reading decreases about 5 °C or
increases up to 90 °C.
8. Acquire a GC chromatogram for your fraction #1 (by your instructor).
9. Turn off the hotplate and cool down the apparatus to the room temperature.
10. Disassemble the apparatus and label the 5 mL conical vial as “Fraction #2”. Again, close
the vial in the same manner as step 7.
11. Acquire a GC chromatogram for your fraction #2.
12. Clean used glassware by rinsing with tap water at the sink and place them back in your
drawer.
13. Unplug the hotplate and clean your workstation.
Notes for the Template:
1.
2.
Do not turn in this first page (which is this page you are looking
at now).
Remove all text inside of the parenthesis as well as the example
paragraphs. Your final write-up shouldn’t contain any parenthesis
except for the ones you choose to add. There will be point
deduction if you still have them in your final, submitted draft.
NAME: (your name)
CHEM 241L
SECTION #: (your section #)
UNLV 2020 Summer Session II
HICKMAN STILL DISTILLATION AND GAS CHROMATOGRAPHY
PURPOSE
(Specifically state the purpose of the experiment and evaluation methods in a few
sentences.)
Example:
The purpose of this experiment is to separate hexane and toluene from a mixture by distillation using
Hickman Still apparatus. After isolation of each component, gas chromatography is used to evaluate the
efficiency of the Hickman distillation technique performed.
PROCEDURE
(Write a paragraph of the detailed experimental procedure including observation in 3rd
person past tense from the experiment video. In this report, do not copy and paste the
lab manual procedure. See the following example for your understanding.)
Example:
316 mg of ferrocene (1.7 mmol) and 2 mL of acetic anhydride were placed in a 10 mL of round-bottom flask,
to this mixture, 10 drops of 85% phosphoric acid was added slowly with stirring. A water-cooling condenser
was attached, and the mixture was heated for 20 minutes in a 90 ˚C water bath. After cooling down, 1.0 mL
of ice-cold water was added dropwise to the reaction mixture. The diluted mixture was poured into a 50 mL
beaker containing about 10 g of ice. The mixture was neutralized by adding approximately 5 g of solid
sodium bicarbonate (about 0.25 g at a time) until the CO 2 stops bubbling off and pH = 5 – 6 with the pH
paper testing. The crude solid product was collected by vacuum filtration and washed thoroughly with cold
water. After determining the mobile phase by TLC, the crude product was purified by column
chromatography using ethyl acetate/hexane (1:9, v/v).
DATA/RESULTS
(Report all collected and calculated data from the experiment video. Fill all necessary
values in the provided table.)
❖ Gas Chromatography Results
Components
Retention
Time
(min)
Height of
the peak
(mm)
Width @
½ height
(mm)
Area
(mm3)
Total
Area
(mm3)
%
Composition
Total
Area
(mm3)
%
Composition
Hexane peak
1
Hexane peak
2
Hexane peak
3
Hexane peak
4
Toluene
(If a peak is invisible or unmeasurable, type “n/a”.)
Components
Hexane peak
1
Hexane peak
2
Hexane peak
3
Hexane peak
4
Toluene
Retention
Time
(min)
Height of
the peak
(mm)
Width @
½ height
(mm)
Area
(mm3)
DISCUSSION & CONCLUSION
(This is the section in which you interpret the data obtained in the previous section. It
demonstrates that you understand and can interpret the data you have collected. Interpret
the data obtained, observations, graphs, etc. and compare with literature sources where
necessary. Relate the experimental results to the theory discussed in the introduction.
This section also addresses the yield and purity of products and possible sources of error
that may have influenced these results.)
(For this experiment, include the following specifics)
– State % composition of each component.
– Which component was distilled first from the mixture? Why?
– How many peaks did you observe on each of the provided chromatograms? What compound does
each peak correspond to?
– Explain how you identified the peaks on the provided GC chromatograms.
– Based on the results of the experiment, evaluate the effectiveness of the Hickman Still distillation
for hexane and toluene separation.
– Suggest any possible improvement in this experiment for the future.
Post-Lab Questions
1. Distillation temperature at an interval of every two minutes during this experiment
was recorded and shown in the table below. Draw a graph of temperature vs. time
using Microsoft Office Excel. Copy and paste the graph in this section.
Time
Temperature
(min)
(°C)
0
24
2
24
4
24
6
24
8
24
10
24
12
24
14
32
16
41
18
52
20
64
22
72
24
72
26
72
28
73
30
73
32
68
34
65
36
63
38
63
40
63
42
63
2. Explain why the distillation temperature started decreasing at 32 minutes in the
graph you drew in the question #1.
3. What is the most important physical property of a compound to determine the
retention time in Gas Chromatography in this experiment?
Fraction 1
Chromatogram
uV
3.310
1SFID1
8000000
7000000
6000000
5000000
4000000
3.208
3.566
4.625
3000000
3.106
2000000
1000000
0
2.50
2.75
3.00
3.25
3.50
3.75
4.00
4.25
4.50
4.75
5.00
min
Fraction 2
Chromatogram
uV
1SFID1
4.621
20000000
17500000
15000000
12500000
10000000
7500000
5000000
2.50
2.75
3.00
3.25
3.50
4.876
3.532
3.274
0
3.168
3.066
2500000
3.75
4.00
4.25
4.50
4.75
5.00
min

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