Ethene, C2H4, is an unsaturated hydrocarbon - Edexcel - GCSE Chemistry - Question 7 - 2019 - Paper 1
Question 7
Ethene, C2H4, is an unsaturated hydrocarbon.
(a) Explain why ethene is an unsaturated hydrocarbon.
(b) A sample of ethene is burned completely in oxygen.
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Worked Solution & Example Answer:Ethene, C2H4, is an unsaturated hydrocarbon - Edexcel - GCSE Chemistry - Question 7 - 2019 - Paper 1
Step 1
Explain why ethene is an unsaturated hydrocarbon.
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Answer
Ethene is considered an unsaturated hydrocarbon because it contains carbon and hydrogen only, and features a double bond between two carbon atoms. This double bond signifies the presence of unsaturation, contrasting with saturated hydrocarbons like alkanes, which contain only single bonds.
Step 2
Write the balanced equation for this reaction.
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Answer
The balanced equation for the complete combustion of ethene is:
ightarrow 2CO_2 + 2H_2O$$
Step 3
Describe what you would see when a sample of ethene and a sample of poly(ethene) are shaken with separate, small volumes of bromine water.
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When bromine water is added to a sample of ethene, the solution would change from brown to colorless due to the addition reaction between ethene and bromine. Conversely, when bromine water is added to poly(ethene), there would be no noticeable change in color, as poly(ethene) is saturated and does not react with bromine.