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HydrocarbonsEdexcel GCSE Chemistry: Flashcards

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What is an alkane?

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What is an alkane?
A hydrocarbon containing only single carbon-carbon bonds (saturated).
Name the first four alkanes and their formulae.
Methane CH4, ethane C2H6, propane C3H8, butane C4H10.
What is an alkene?
A hydrocarbon containing at least one C=C double bond (unsaturated).
What is the functional group of alkenes?
C=C (carbon-carbon double bond).
Why are alkanes described as saturated?
Because they contain only single bonds, so their carbon atoms hold the maximum possible number of hydrogen atoms.
What type of reaction occurs between ethene and bromine?
An addition reaction — bromine adds across the C=C double bond to form 1,2-dibromoethane.
How is bromine water used to distinguish alkanes from alkenes?
Bromine water is decolourised by alkenes (addition reaction) but stays orange/brown with alkanes (no reaction).
What are the products of complete combustion of a hydrocarbon?
Carbon dioxide and water, with energy released.
Name the alkenes required by the spec.
Ethene, propene, but-1-ene, but-2-ene.
What is the molecular formula shared by but-1-ene and but-2-ene?
C4H8 — they differ only in the position of the double bond.
Is complete combustion of an alkene an oxidation reaction?
Yes — the hydrocarbon is oxidised to carbon dioxide and water.