The test for unsaturated compounds
3 marks · EasyA student compares the reaction of different alkenes with bromine water. The results are shown in the table.
| Alkene tested | Observation with bromine water |
|---|---|
| ethene | colourless |
| propene | colourless |
| but-1-ene | colourless |
Describe the pattern in the results.
State a conclusion about the reaction between alkenes and bromine water.
Suggest what would happen if pent-1-ene was tested with bromine water.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) All alkenes tested cause bromine water to become colourless.
(b) All alkenes react with bromine water in an addition reaction, decolourising it.
(c) Bromine water would also become colourless with pent-1-ene.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly describes pattern: all alkenes make bromine water colourless.
B1 (b) · 1 mark · States correct conclusion: all alkenes react with bromine water and decolourise it.
B1 (c) · 1 mark · Predicts that pent-1-ene would also decolourise bromine water / make it colourless.
Worked solution
(a) All the alkenes tested make bromine water colourless.
(b) All alkenes react with bromine water and decolourise it in an addition reaction.
(c) Pent-1-ene would also make bromine water colourless.