Question

Give a chemical test to distinguish between ethane and ethene.

Answer 1

Hint: Put both the samples in separate test tubes and dissolve them in carbon tetrachloride solution. Carbon tetrachloride is a non-polar solvent. When we pass bromine gas from both the test tubes and observe the changes taking place in the test tube.

Complete answer:
Take ethane and ethene in two separate test tubes and dissolve them in carbon tetrachloride solution. Pass bromine gas into the two test tubes. If the color of bromine gas is discharged, then that gas is ethene and if the color of gas remains the same, then that test tube contains ethane gas. Ethane is an alkane and is saturated. If a compound is saturated, it means all the bonds in the compound are single bonds. Ethene is an alkene and is unsaturated because it contains carbon-carbon double bonds. When we add bromine to ethene, the color of bromine gets discharged because bromine attacks the double bonds present in alkene to form bromoalkane. So, the bromine is used up and the color disappears. Ethane is a saturated hydrocarbon and has only single bonds. So, it does not react with bromine and the color of bromine remains the same in the test tube containing ethane.

Note:
Remember that bromine is used to test unsaturation in hydrocarbons. Bromine solution is brown in color. When bromine solution is added to the unsaturated hydrocarbon the brown color disappears if the hydrocarbon is an unsaturated hydrocarbon.