21. Preparation of Ethyne
Summary
TLDRThis educational video demonstrates the preparation and examination of ethyne (C2H2), a colorless gas with a pungent odor. Ethyne is synthesized from calcium carbide, which often contains impurities like calcium sulfide and phosphide. The resulting ethyne gas is purified by passing it through acidified copper sulfate to remove contaminants. The video outlines safety precautions, such as avoiding contact with calcium carbide and using no open flames. It also covers tests for ethyne's properties, including its insolubility in water, solubility in organic solvents, and its reactivity with bromine and potassium permanganate, which indicate the presence of a carbon-carbon triple bond.
Takeaways
- π¬ Ethine (C2H2) is prepared by reacting water with calcium carbide (CaC2), also known as calcium dicarbide.
- β οΈ Calcium carbide is often impure, containing contaminants like calcium sulfide, phosphide, and nitride, which can affect the purity of ethine.
- π¬οΈ The ethine produced may contain impurities such as hydrogen sulfide, phosphine, and ammonia, which are removed by passing the gas through acidified copper(II) sulfate.
- π Handle calcium carbide with care, using a spatula to avoid initiating the reaction with moisture from hands.
- π« Keep naked flames away from the gas preparation apparatus due to the risk of explosion when ethine mixes with air.
- π Ensure the gas washing bottle is correctly connected to prevent impure gases from being collected.
- π§ Add water slowly to calcium carbide to control the rate of ethine production.
- π§ͺ Ethine is a colorless gas that may have an unpleasant smell if impurities are present, and it is insoluble in water but soluble in organic solvents.
- π₯ Ethine burns with a luminous, smoky flame and produces soot, indicating the presence of unburned carbon.
- π The addition of bromine water to ethine decolorizes the solution, demonstrating the reaction of the carbon-carbon triple bond with bromine.
- π£ Acidified potassium permanganate solution also decolorizes in the presence of ethine, showing another test for unsaturation due to the reactive triple bond.
Q & A
What is ethine and what is its chemical formula?
-Ethine is a compound with the chemical formula C2H2, also known as acetylene.
What is the primary reactant used to prepare ethine in the described experiment?
-The primary reactant used to prepare ethine in the experiment is calcium carbide (CaC2), also known as calcium dicarbide.
Why is calcium carbide often contaminated with other substances?
-Calcium carbide is often contaminated with substances like calcium sulfide, calcium phosphide, and calcium nitride because it cannot be obtained in a pure state.
What are the safety precautions when handling calcium carbide?
-When handling calcium carbide, one should not touch it with bare hands to avoid initiating the reaction with moisture, and a spatula should be used for transferring it. Also, no naked flame should be brought near the gas preparation apparatus due to the risk of explosion.
How are impurities in ethine gas removed during the experiment?
-Impurities in ethine gas are removed by bubbling the gas through acidified copper(II) sulfate.
What is the purpose of the gas washing bottle in the experiment setup?
-The gas washing bottle is used to ensure that the ethine gas is clean and free of impurities before it is collected and tested.
What physical properties of ethine are mentioned in the script?
-Ethine is described as a colorless gas that is insoluble in water but soluble in organic solvents.
How is the combustion test for ethine performed, and what is observed?
-The combustion test is performed by bringing a lit taper to the mouth of a gas jar containing ethine. It burns with a luminous, smoky flame, and a great deal of soot is formed due to unburned carbon.
What happens when ethine reacts with bromine water, and why?
-When ethine reacts with bromine water, the yellow color disappears because the very reactive carbon-carbon triple bond in ethine reacts readily with the bromine.
What is the purpose of adding acidified potassium permanganate to ethine, and what is observed?
-Adding acidified potassium permanganate to ethine is used to test for unsaturation. The purple color of the potassium permanganate disappears, indicating a reaction with the carbon-carbon triple bond in ethine.
Why is it important to perform tests on ethine away from the apparatus?
-Tests on ethine should be performed away from the apparatus because ethine gas forms an explosive mixture with air, and conducting tests near the apparatus could be dangerous.
Outlines
π¬ Preparation and Collection of Ethyne
The video script describes an experiment to prepare ethyne (C2H2) by reacting water with calcium carbide (CaC2), also known as calcium dicarbide. It is noted that calcium carbide is often contaminated with other compounds like calcium sulfide, phosphide, and nitride, which can contaminate the ethyne with gases such as hydrogen sulfide, phosphine, and ammonia. To purify the ethyne, the gas is bubbled through acidified copper(II) sulfate. The setup of the experiment is detailed, emphasizing safety precautions such as avoiding contact with calcium carbide and not using naked flames near the apparatus due to the explosive nature of ethyne when mixed with air. The process involves adding water slowly to calcium carbide to produce ethyne, which is collected in test tubes and gas jars. The reaction's equation is displayed on the screen.
π Testing the Properties of Ethyne
This part of the script focuses on testing the physical properties and reactions of ethyne. It is observed that ethyne is a colorless gas, which may have an unpleasant smell if impurities are present. Unlike methane, ethyne is insoluble in water but soluble in organic solvents. A combustion test is conducted, where ethyne burns with a luminous, smoky flame, producing soot due to unburned carbon. The script also details tests for unsaturation in ethyne: the addition of bromine water, which decolorizes indicating a reaction with the carbon-carbon triple bond, and the addition of acidified potassium permanganate, which also decolorizes due to the same reactive bond. The script clarifies that the specific reaction equations and product names are not required knowledge for the course, and thus, they are not discussed further. The segment concludes with a summary of the study on the properties of ethyne.
Mindmap
Keywords
π‘Ethine
π‘Calcium Carbide
π‘Copper(II) Sulfate
π‘Combustion
π‘Bromine Water
π‘Potassium Permanganate
π‘Carbon-Carbon Triple Bond
π‘Flask
π‘Fume Cupboard
π‘Spatula
π‘Impurities
Highlights
Ethine (C2H2) is prepared by the reaction of water with calcium carbide (CaC2).
Calcium carbide is contaminated with calcium sulfide, phosphide, and nitride, affecting ethine purity.
Impurities in ethine include gases like hydrogen sulfide, phosphine, and ammonia.
Acidified copper(II) sulfate is used to remove impurities from ethine gas.
Apparatus setup instructions emphasize safety, avoiding contact with calcium carbide and naked flames.
Ethine gas forms an explosive mixture with air, necessitating careful handling.
Gas washing bottle connections must be double-checked for safety.
The reaction equation for ethine formation is displayed during the experiment.
Physical properties of ethine include being colorless, smelling unpleasant if impure, and insoluble in water.
Ethine is soluble in organic solvents due to its chemical structure.
Combustion tests of ethine show a luminous, smoky flame with soot formation.
Bromine water test indicates ethine's unsaturation by the disappearance of the yellow color.
The addition of acidified KMnO4 to ethine results in a colorless solution, demonstrating unsaturation.
The carbon-carbon triple bond in ethine is very reactive and readily reacts with bromine and potassium permanganate.
Students are not required to know the reaction equations or product names for the bromine and KMnO4 tests.
The study concludes with an overview of ethine's properties and the experimental procedures.
Transcripts
[Music]
experiment to prepare ethine and examine
its
properties ethine C2 H2 is prepared by
the reaction of water with a substance
called calcium carbide
ca2 calcium carbide is also called
calcium
dicarbide calcium carbide cannot be
obtained in a pure state it is usually
contaminated with calcium sulfide
calcium phosphide and calcium nitride as
a result the ethine obtained from it
usually is contaminated with gases like
hydrogen sulfide phosphine and
ammonia these gases are removed by
bubbling the gas through acidified
copper 2
sulfate set up the apparatus as
shown do not touch the calcium carbide
with your fingers as moisture from your
hands could start the reaction
use the spatula when transferring the
calcium carbide to the
flask no naked flame should be brought
anywhere near the gas preparation
apparatus ethine gas forms an explosive
mixture with air tests on the gas should
be performed well away from the
apparatus
double check that you have connected the
gas washing bottle
correctly
using the dropping funnel Add Water
slowly to the calcium carbide to
maintain an even not too vigorous
evolution of
etin
collect some test tubes and a few gas
jars of the
gas
for
e
just
the equation for the reaction is shown
on the
screen note the formation of white
calcium hydroxide inside the flask place
your hand on the outside of the
flask when you perform this experiment
yourself
write down what you
notice in the next part of the
experiment we will carry out a number of
tests on the
gas note the physical properties of
ethine it is a colorless gas with the
smell if impurities are still present it
will not smell very
nice like methane and
ethine ethine is insoluble in water but
soluble in organic
solvents
combustion if your teacher allows it
bring the gas jar of ethine to the fume
cupboard remove the gas jar cover and
apply a lighted taper to the mouth of
the gas
chair note that it burns with a luminous
Smoky flame and a great deal of soot is
formed the so is formed as a result of
unburned
carbon addition of bromine as in the
case of the preparation of ethine
bromine can be used to test for
unsaturation at about 110 of a test tube
of broing water to a test tube of
ethine replace the stopper and shake the
test tube a few
times note that the yellow color
disappears the very reactive
carboncarbon triple bond reacts readly
with the
you are not required to know the
equation of the reaction or the names of
the products for this
course addition of acidified
km4 as in the case of the preparation of
ethane potassium permanganate can be
used to test for
unsaturation add about one1 of a test
tube of potassium permanganate to a test
tube of
e replace the stopper and shake the test
tube a few times
note that the purple color disappears
and a colorless solution is
obtained the very reactive carboncarbon
triple bond reacts readly with the
potassium
permanganate you are not required to
know the equation of this reaction are
the names of the products for this
course hence it will not be discussed
further this concludes the study of the
properties of
ethine
[Music]
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