Unsaturated hydrocarbons contain multiple bonds between the two C-atoms and show addition reaction. Give the test to distinguish ethane from ethene.

Explanation

Bromine solution in `C Cl_(4)` has an orange colour. When it is added dropwise to ethene, the orange colour disappears due to the formation of the colourless ethylene dibromide. This reaction is not shown by ethane as it is addition reaction.
`underset("Ethene")(CH_(2)=CH_(2))underset(("orange"))underset("Bromine")(+Br_(2))tounderset(("colourless"))underset("Ethylene dibromide")underset(Br)underset(|)(CH_(2))-underset(Br)underset(|)CH_(2)`
The two can be distinguished also by subjecting them to the flame. Saturated hydrocarbon (ethane) generally gives a clear flame while unsaturated hydrocarbon (ethene) gives a yellow flame with lots of black smoke.