Ethene (C₂H₄) and ethyne (C₂H₂) are unsaturated hydrocarbons - Leaving Cert Chemistry - Question 1 - 2006
Question 1
Ethene (C₂H₄) and ethyne (C₂H₂) are unsaturated hydrocarbons. They can both be easily prepared in a school laboratory.
(a) The diagram on the right shows an apparat... show full transcript
Worked Solution & Example Answer:Ethene (C₂H₄) and ethyne (C₂H₂) are unsaturated hydrocarbons - Leaving Cert Chemistry - Question 1 - 2006
Step 1
Identify solid A which is used to keep the ethanol at the end of the test tube.
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Answer
The solid A is identified as glass wool or rock wool, which is used to provide insulation and to keep the ethanol in the test tube.
Step 2
Give the name or formula of solid B which is heated using the Bunsen burner.
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Solid B is aluminum oxide (Al₂O₃), which acts as a catalyst in the reaction to produce ethene gas.
Step 3
What precaution should be taken when heating is stopped? Why is this necessary?
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When heating is stopped, it is important to remove the delivery tube from the trough or dismantle the apparatus to prevent back-suction or the contamination of the reagents. This ensures safety during the experiment.
Step 4
Give one major use of ethene gas.
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One major use of ethene gas is in the manufacture of polyethylene, which is widely utilized in plastic production.
Step 5
Identify X and liquid Y, the reagents used in the preparation.
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X is identified as calcium carbide (CaC₂) and liquid Y is water (H₂O), which react to produce ethyne gas.
Step 6
Describe what you would observe when a sample of ethyne gas is generated.
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Upon generating ethyne gas, you would observe a luminous flame when the gas is ignited, indicating a rich acetylene flame due to carbon combustion.
Step 7
Give one major use of ethyne gas.
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One major use of ethyne gas is in welding torches due to its high flame temperature, facilitating cutting and joining of metals.
Step 8
Describe a test you could carry out on either of the two gases to show that it is unsaturated. What would you observe during the test?
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A test that can be conducted is to add bromine solution to either ethene or ethyne gas. When the unsaturated gas is present, the reddish-brown color of the bromine will decolorize, indicating the reaction with the double or triple bonds in the hydrocarbons.
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