20. Preparation of Ethene
Summary
TLDRThis experiment focuses on the preparation and examination of ethene, a colorless gas, by dehydrating ethanol using aluminum oxide as a dehydrating agent and catalyst. The process involves heating ethanol in a boiling tube, collecting ethene gas over water, and observing its properties. Ethene's insolubility in water, combustion to form carbon dioxide and water, and reactivity with bromine water and potassium permanganate are demonstrated, confirming the presence of a carbon-carbon double bond.
Takeaways
- 🧪 The experiment involves preparing a sample of ethene gas by dehydrating ethanol using aluminum oxide (Al2O3) as a dehydrating agent and catalyst.
- 🔥 A Bunsen burner is used to gently heat the aluminum oxide, which initiates the dehydration reaction at the end of the boiling tube where ethanol is held by glass wool.
- 🌡️ The boiling tube is positioned horizontally to ensure the ethene gas produced can be collected over water.
- 💧 Ethene is insoluble in water, which is demonstrated by its ability to be collected over water without dissolving.
- 🔥 Ethene burns with a flame, indicating it is flammable, and when burned in air, it forms carbon dioxide and water.
- 🥛 The presence of carbon dioxide after burning ethene is confirmed by adding limewater, which turns milky due to the formation of calcium carbonate.
- 🌿 Bromine water is used to test for unsaturation in organic compounds; the disappearance of the yellow color indicates the presence of a carbon-carbon double bond in ethene.
- 🧪 The addition of bromine across the double bond in ethene results in the formation of a colorless compound, 1,2-dibromoethane.
- 🌿 Potassium permanganate (KMnO4) is also used as a test for unsaturation, and its decolorization upon reaction with ethene confirms the presence of a carbon-carbon double bond.
- 📚 The experiment concludes with a demonstration of the chemical properties of ethene, highlighting its reactivity due to the presence of a carbon-carbon double bond.
Q & A
What is the purpose of the experiment described in the transcript?
-The purpose of the experiment is to prepare a sample of ethene gas by dehydrating ethanol using a chemical reaction and to examine its properties.
Which substance is used as a dehydrating agent and catalyst in the experiment?
-Aluminium oxide (Al2O3) is used as a dehydrating agent and catalyst in the experiment.
How is the boiling tube positioned during the reaction?
-The boiling tube is clamped near its mouth and positioned horizontally during the reaction.
What is the role of glass wool in the experiment?
-Glass wool is used to hold the ethanol in place while the reaction takes place.
How is the gas collected in the experiment?
-The gas is collected over water, indicating that ethene is insoluble in water.
What happens when ethene is burned?
-When ethene is burned, it produces a flame and carbon dioxide, which turns limewater milky.
What is the significance of the color change in bromine water when added to ethene?
-The disappearance of the yellow color in bromine water indicates the presence of unsaturation, such as a carbon-carbon double bond, in the ethene molecule.
How does potassium permanganate (KMnO4) test for the presence of a carbon-carbon double bond in ethene?
-The disappearance of the purple color of potassium permanganate to give a colorless solution is evidence for the presence of a carbon-carbon double bond in ethene.
What is the expected product when bromine is added to ethene?
-The expected product when bromine is added to ethene is a colorless oily compound called 1,2-dibromoethane.
Why is it important to remove the delivery tube from the water after collecting the gas?
-It is important to remove the delivery tube from the water to prevent a siphoning effect, which could occur if the boiling tube cools and the water is sucked back into the tube, potentially causing it to crack.
What general rule is followed when organic compounds like ethene burn in air?
-When organic compounds like ethene burn in air, they generally form carbon dioxide and water.
Outlines
🔬 Preparing Ethane Gas from Ethanol
In this segment, the experiment focuses on preparing a sample of ethane gas by dehydrating ethanol. Ethanol is dehydrated using a chemical reaction facilitated by aluminum oxide (Al2O3), which acts as both a dehydrating agent and a catalyst. The process begins with pouring ethanol into a boiling tube, adding glass wool to contain the liquid, and then placing aluminum oxide along the tube. The setup includes a Bunsen burner for heating and a collection apparatus for capturing the gas. The reaction is initiated by heating the aluminum oxide, which in turn heats the ethanol, causing it to vaporize and react with the aluminum oxide to form ethane gas. The gas is collected over water, indicating that ethane is insoluble in water. The experiment also involves careful handling to prevent air bubbles and to ensure the collection of pure ethane gas samples.
🔍 Investigating the Properties of Ethane
This part of the experiment investigates the physical properties of ethane, a colorless and odorless gas. The insolubility of ethane in water is demonstrated by its ability to be collected over water. The experiment proceeds to examine the combustion of ethane, noting that it burns with a characteristic flame and produces carbon dioxide, which is confirmed by the limewater turning milky. The presence of a carbon-carbon double bond in ethane is tested using bromine water and potassium permanganate (KMnO4). The addition of bromine water to ethane results in a colorless compound, indicating the formation of 1,2-dibromoethane, and the disappearance of the bromine water's yellow color signifies the presence of unsaturation in the ethane molecule. Similarly, the addition of potassium permanganate and its subsequent decolorization provides further evidence of the carbon-carbon double bond in ethane.
Mindmap
Keywords
💡Ethanol
💡Dehydration
💡Aluminium Oxide (Al2O3)
💡Boiling Tube
💡Glass Wool
💡Bunsen Burner
💡Gas Collection Over Water
💡Bromine Water
💡Potassium Permanganate (KMnO4)
💡Carbon-Carbon Double Bond
💡Lime Water
Highlights
Preparation of a thin gas sample by dehydrating ethanol using a chemical reaction.
Use of aluminum oxide (Al2O3) as a dehydrating agent and catalyst in the reaction.
Ethanol is dehydrated to form a new substance over heated aluminum oxide.
Collection of the gas over water, indicating the gas is insoluble in water.
Burning of the gas produces a blue flame, indicating it is an alkene.
Addition of lime water turns milky, confirming the formation of carbon dioxide upon burning.
Bromine water decolorization upon reaction with the gas, indicating the presence of unsaturation.
Formation of a new colorless compound, 1,2-dibromoethane, upon addition of bromine.
Use of potassium permanganate to test for the presence of carbon-carbon double bonds.
Disappearance of purple color in potassium permanganate solution confirms the presence of a double bond.
General rule that organic compounds burn in air to form carbon dioxide and water.
Reactivity of alkenes due to the presence of carbon-carbon double bonds.
Bromine adds across the carbon-carbon double bond to form 1,2-dibromoethane.
Bromine water is commonly used as a test for unsaturation in compounds.
The study concludes with the successful identification of the properties of the alkene.
Transcripts
experiments to prepare eating and
examine its properties in this
experiment we will prepare a sample v
thin gas by dehydrating a substance
called ethanol others using a chemical
reaction to remove the elements of water
from ethanol a white powder called
aluminium oxide al2o3 is used in to
reaction this substance acts as a
dehydrating agent and also as catalyst
the reaction some ethanol was poured
into a boiling tube to a depth of about
two to three centimeters some glass wool
was added to soak up the ethanol glass
wool is used to hold the ethanol in
place while the reaction to produce at a
theme is a crane using a retort stand
the boiling tube is camp near its most
and in a horizontal position as shown
using a spatula a heap of aluminium
oxide is placed about halfway along the
boiling tube the apparatus collecting
gas is set up as shown and the gas is
collected over watering light the Bunsen
burner
adjusted to give a brief flame and
gently heat the aluminum oxide
at the aluminum oxide comes fast the
heat reaches the ethanol at the end of
the tube the a smell changes into a
vapor passes over the heart aluminium
oxide and is dehydrated form a scene if
the e teen is bubbling off T slowly
moved once in Burnet near the edge now
for a bridge moment allow the bubbles to
escape for a short one as these are
mainly bubbles of air displaced from the
apparatus
collect five tattoos of the gas
put a stopper on each test tube as it is
filled
when all the test Chiefs have been
filled leasing the boss head on the
reach our stand and raise the apparatus
up so that the delivery cheap is no
longer dipping into the water then turn
off the Bunsen burner if the delivery
cheap were simply left in the water
trust a suck lack of water would occur
since the boiling tube begins to cool as
soon as the Bunsen burner is turned off
the cold water could cause the hot
boiling tube to crack in the next part
of this experiment we will examine
proxies VP note the physical properties
of eating it is the colorless gas with
Swedish Sloan the fact that the gas can
be collected over water shows clearly
that is insoluble in water otherwise gas
would simply dissolve in the water
instead the bubble insurance we now
investigate what happens when we burn
easy remove the lid from one of the gas
chains and use the latest wax paper
apply a light the most of the gas turn
note that the gas burns would leave them
the flame allow the gas to burn when it
is soft burning add some lame water to
the gas sir
replace the lid and shake the gas share
a few times
limewater turns milky showing the carbon
dioxide has been formed when a teen
burns an area eating burns to form
carbon dioxide mortar accordance with
equations shown on screen as a general
rule or organic compounds burn and air
to form carbon dioxide and water
addition of bromine alkenes are more
reactive than alkenes because of the
presence of the carbon-carbon double
bond in alkenes
for example bromine adds across the
carbon-carbon double bond to form a
colourless oily compound called one to
die bromomethane a solution of bromine
and water is commonly called bromine
water let's see what happens if we add
some bromine water to a test tube of
eating replace the stopper and shake the
test tube a few times
note that the yellow color of the Birman
water solution disappears what happens
here is that a new colorless compound
called to bromo ethanol is formed the
loss of the yellow color from bromine is
standard test for unsaturation in a
compound in other words this test shows
us that there is either carbon carbon
double bonds or a carbon-carbon triple
bond in the ec molecule potassium
permanganate kmno4 is also used to test
for the presence of the carbon-carbon
double bond anything add about 1/10 of
test tube of dilute kmno4 to a test tube
of 18 shake the test tube a few times
the disappearance of prayerful colors to
give the colorless solution is evidence
for the presence of a carbon-carbon
double bond this concludes the study of
proxies movie theme
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