The document describes an experiment to synthesize ethene gas by dehydrating ethanol using aluminum oxide as a catalyst and then testing the product gas through addition, oxidation, and combustion reactions. The experimental results showed that bromine water lost its color in an addition reaction, potassium permanganate solution turned brown in an oxidation reaction, and the gas burned when exposed to a flame through combustion. The aim of producing ethene gas from ethanol and observing characteristic alkene reactions was achieved based on the results.

1. Synthesis of ethene – Dehydration of ethanol
1. Introduction
Aim:
To investigate the synthesis of ethene through the dehydration of ethanol and to test the
product produced using some tests that are characteristic to unsaturated hydrocarbons.
Hypothesis:
Write a suitable hypothesis that corresponds to the aim of the experiment.
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Example answer:
Ethene gas will be formed from the dehydration of ethanol and different reactions that
are characteristic to the alkene will occur in two of the three test tubes, with the third
test illustrating one of the properties of ethene. The reactions that will occur are
addition, oxidation and combustion.
Note: All example answers for this experiment are in italics.
2. Method
Apparatus and materials list and diagrams:
Materials List
Wire wool Water Heat mat
4 test tubes Large beaker or trough Bunsen burner
100mL small beaker 5 drops of bromine water (Br2) Ethanol
Aluminum oxide 5 drops of cold dilute Stopper with attached
(Al2O3) potassium permanganate delivery tube
solution (KMnO4)
Retort stand or Candle Retort stand clamp
wooden clamp
3 stoppers Matches
Note:
Ethanol is highly flammable and bromine water can be harmful to the skin if in contact
for long periods. Bromine vapour from bromine water can also be harmful if inhaled.
Therefore, it is best to wear gloves and go under the fumehood when carrying out the
bromine part of the experiment.

2. Safety goggles must be worn throughout the experiment. Unfortunately.
Diagrams:
Figure 11: Set up of experiment.
Sequential Steps:
1. Label three test tubes A, B and C.
2. Grab a fourth test tube and place a small ball of wire wool in the bottom of that
test tube. Ensure that the wire wool only covers 1-2cm of the test tube and isn’t
too compressed.
3. Pour a small amount of ethanol into the test tube from a beaker, just enough to
cover the wire wool and allow the ethanol to soak into the wire wool.
4. Slowly tip the ethanol in the test tube back into the beaker while making sure that
the wire wool remains at the bottom of the test tube.
5. Fill the test tube with approximately 5cm of aluminium oxide.
6. Seal the test tube with the stopper that has the attached rubber hose and either
attach the test tube to a retort stand or clamp it with a wooden clamp.
7. Fill up a trough/beaker and test tubes A,B and C with water. Invert test tube A so
that it is semi-submerged in the trough and set up the experiment as shown in
figure 1.
8. Heat the part of the test tube that contains the aluminium oxide until enough
ethene gas is collected in test tube A. While keeping the Bunsen burner on and in
place (so that no suck-back occurs), remove test tube A and quickly seal it with a
stopper. Repeat this heating procedure for test tubes B and C, also sealing them
with stoppers after collection of the gas.
9. Add 5 drops of bromine water (Br2(aq)) to the gas in test tube A and replace the
stopper quickly after. Note down in table 1 any observations on the original and
final colour of the solution.
10. In test tube B add 5 drops of potassium permanganate solution (KMnO4) and
replace the stopper quickly after. Record any observations.
11. Light a candle, turn test tube C upside down and bring the flame close to the edge
of the test tube. Record any observations.

3. 3. Results
Table 1. Qualitative Results
Test Observations
Tube
A
B
C
Table 1. Qualitative Results
Test Observations
Tube
A Original colour of bromine water - yellow/orange. After a few
minutes bromine lost its colour. Final colour - pale yellow
and almost clear. The liquid appears oily.
B Original colour of Potassium permanganate – purple. Final
colour - Brown solution with precipitate in the liquid. Yellow
stains were observed on the test tube around the solution.
C A yellow flame was observed. The gas burned at the edges of
the test tube.
4. Discussion
Comparison of theoretical and experimental results:
Compare your qualitative experimental results for each test tube to the theoretical
results/information in the ‘properties of ethene’ section of your notes. Do your
experimental results comply with the theoretical results?
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Yes. The experimental results comply with the theoretical results as in test tube A the
bromine lost its colour and became pale, in test tube B the purple colour of potassium

4. permanganate turned into a brown solution and a flame was observed at the edges of
test tube C.
Questions:
1. Write the equation for the synthesis of ethene through the dehydration of
ethanol with the organic compounds written in their skeleton structure form.
Equation for the dehydration of ethanol.
Al2O3
Dehydration of ethanol
occurs under the catalyst aluminium
oxide to form ethene and steam.
2. Explain and state the reaction that occurred in test tube A.
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An addition reaction occurred in test tube A. The bromine water which was
originally a yellow/orange colour lost its colour and became pale yellow after
reacting with ethene. The double bond in ethene was broken and 1,2-
dibromoethane was formed. This process is also known as halogenation.
3. Explain and state the reaction that occurred in test tube B.
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An oxidation reaction occurred in test tube B. The purple potassium
permanganate turned brown with precipitate after being added to ethene. This
is oxidation reaction is characteristic to an alkene, and a dialcohol is formed.
The colour of the end solution is dependent on the pH conditions of the
potassium permanganate. Since the product was a brown solution with
precipitate it can be said that the potassium permanganate solution must have
been slightly diluted with an alkaline.

5. 4. Name the type of reaction that occurred in test tube C and write a balanced
equation for the reaction.
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The reaction was a combustion reaction.
Equation for the reaction in test tube C.
C2H4 (g) + 3O2 (g) 2CO2 (g) + 2H2O (g)
Ethene undergoes combustion and forms carbon dioxide and water vapour.
5. Suggest some other substances other than aluminium oxide that could be used
as a catalyst for the dehydration of ethanol.
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Sulphuric acid and zeolites are commonly used as catalysts in the manufacture
reaction of ethene from the dehydration of ethanol.
Conclusion
Write a suitable conclusion which incorporates the aim and your hypothesis. Ensure
that a comparison is made to your hypothesis.
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Ethene was synthesized from the dehydration of ethanol and was then reacted with
various reagents to undergo addition, oxidation and combustion reactions as
hypothesized.

6. Bibliography
1) Clark, Jim 2003, Oxidation of alcohols, viewed 1st of October 2010,
<http://www.chemguide.co.uk/organicprops/alcohols/dehydration.html>
2) The Nuffield Foundation and Royal Society of Chemistry 2010, Dehydration of
Ethanol to form ethene, viewed 1st of October 2010,
<http://www.practicalchemistry.org/experiments/dehydration-of-ethanol-to-
form-ethene,237,EX.html>