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You are provided with three unlabelled tubes containing colourless liquids. One contains an alkene, one an alkane and one water. Describe test-tube reactions that you could carry out to identify each substance. (6 marks)

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User Chris SH
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Step-by-step explanation:

To identify the contents of the three unlabelled test tubes, you could carry out the following test-tube reactions:

To identify the alkene:

Add bromine water (dilute aqueous solution of bromine) dropwise to each test tube. The alkene will react with the bromine water and decolourize it, giving a clear solution. The alkane and water test tubes will not show any reaction.

To identify the alkane:

Add a few drops of a concentrated sulfuric acid to each test tube. The alkane will not react with the sulfuric acid, and there will be no observable reaction. The alkene and water test tubes will show no reaction or some reaction, but not as significant as the alkane test tube.

To identify water:

Add a few drops of anhydrous copper (II) sulfate to each test tube. The anhydrous copper (II) sulfate will react with any water present in the test tube and turn blue. The alkane and alkene test tubes will not show any reaction with copper (II) sulfate.

By performing these test-tube reactions, you should be able to identify which test tube contains an alkene, an alkane, and water.

User Alaa Masoud
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