(i) Give a chemical test to distinguish between saturated and unsaturated hydrocarbon.
(ii) Name the products formed when ethane burns in air. Write the balanced chemical equation for the reaction showing the types of energies liberated.
(iii) Why is reaction between methane and chlorine in the presence of sunlight considered a substitution reaction?
(i) Reaction to distinguish between saturated and unsaturated hydrocarbons
The chemical test that can distinguish between saturated and unsaturated hydrocarbons is Bromine water test .
Since unsaturated hydrocarbons can undergo addition reaction, they react with bromine water and decolorise it. However, saturated hydrocarbons are unable to undergo addition reaction so they do not react with bromine and the brown colour of bromine water remains as it is.
(ii) On burning ethanol in air, combustion takes place and the reaction equation is:
- The products formed as a result of the reaction are carbon dioxide and water.
- The energies liberated are heat and light.
(iii) The reaction between methane and chlorine is considered as a substitution reaction because the hydrogen atoms are replaced by chlorine atoms one by one.
Reaction of Methane with Chlorine