To distinguish butene from pentane, you can use a chemical test based on their different reactivity due to the presence of a double bond in butene (an alkene) and the absence of such a bond in pentane (an alkane). One effective method is to use bromine water or potassium permanganate solution as a test.
Bromine Water Test:
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Reagents Needed:
- Bromine water (a dilute solution of bromine in water, typically brown in color).
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Procedure:
- Take a small amount of the butene and pentane in separate test tubes.
- Add a few drops of bromine water to each test tube.
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Observation:
- Butene: The brown color of bromine water will disappear, indicating the addition of bromine across the double bond of butene. This will result in the formation of a dibromide compound.
- Pentane: There will be no color change because pentane does not react with bromine water, as it lacks a double bond.
Potassium Permanganate Test (Baeyer Test):
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Reagents Needed:
- Dilute potassium permanganate solution (KMnO4), commonly known as "Baeyer’s reagent," which is purple in color.
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Procedure:
- Again, take separate samples of butene and pentane in test tubes.
- Add a few drops of dilute potassium permanganate solution to each test tube.
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Observation:
- Butene: The purple color of potassium permanganate will disappear, changing to a light brown or colorless solution due to the formation of manganese dioxide (MnO2) as butene is oxidized.
- Pentane: No change in color will be observed, as pentane does not react with potassium permanganate.
Conclusion:
Using either the bromine water test or the potassium permanganate test, you can effectively distinguish butene from pentane based on their different reactivities towards these reagents.