1. Ethyne (acetylene) gas (C2H2) is the first member of a homologous series of unsaturated hydrocarbons - Leaving Cert Chemistry - Question 1 - 2014
Question 1
1. Ethyne (acetylene) gas (C2H2) is the first member of a homologous series of unsaturated hydrocarbons. The diagram below shows the arrangement of apparatus used fo... show full transcript
Worked Solution & Example Answer:1. Ethyne (acetylene) gas (C2H2) is the first member of a homologous series of unsaturated hydrocarbons - Leaving Cert Chemistry - Question 1 - 2014
Step 1
Explain the term hydrocarbon.
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A hydrocarbon is a chemical compound that consists entirely of hydrogen (H) and carbon (C) atoms. These compounds can vary in structure and form, encompassing aliphatic, aromatic, saturated, and unsaturated types.
Step 2
To which homologous series does ethyne belong?
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Ethyne belongs to the alkyne series of hydrocarbons. Alkynes are characterized by having at least one carbon-carbon triple bond within their molecular structure.
Step 3
Identify the liquid A.
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The liquid A is water.
Step 4
Identify the solid B.
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The solid B is calcium carbide (CaC2).
Step 5
Identify the liquid C.
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The liquid C is water.
Step 6
Why should the first few test-tubes of gas collected be discarded?
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The first few test-tubes of gas collected should be discarded because they may contain mostly displaced air and impurities, which do not represent the ethyne gas being produced.
Step 7
What is meant by saying that ethyne is unsaturated?
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Ethyne is described as unsaturated because it contains at least one triple (multiple) carbon-to-carbon bond, which is a characteristic of unsaturated hydrocarbons.
Step 8
Describe a test that would show that ethyne is an unsaturated compound.
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To test for the presence of unsaturation, shake the ethyne gas with a bromine water solution (identified reagent) or an acidified potassium permanganate solution. If unsaturation is present, a color change will occur in the solution, indicating the reaction.
Step 9
Describe the flame observed when a test-tube of ethyne is burned in air.
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The flame produced when ethyne is burned in air is very hot and luminous, characterized by a smokey or sooty appearance. This high temperature can exceed 3000 °C.
Step 10
Give a use for this very hot flame.
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A very hot flame produced from burning ethyne can be used for cutting metals or for welding purposes, taking advantage of its high temperature.
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