(a) Substitution reaction is a characteristic of saturated hydrocarbons (alkanes). It is the reaction in which one or more hydrogen atoms of a hydrocarbon are replaced by other atoms.
Methane reacts with chlorine in the presence of sunlight to form chloromethane and hydrogen chloride. In this reaction, the hydrogen atom from methane is replaced by the chlorine atom.
The chemical equation for the above reaction is as follows:
CH4 + Cl2 → CH3Cl + HCl
(b) An oxidising agent is a reactant which readily transfers oxygen atoms to another substance by reducing itself in the process. Two oxidising agents which can oxidise ethanol to ethanoic acid are alkaline potassium permanganate (KMnO4) and acidified potassium dichromate (K2Cr2O7).
(c) Ethanoic acid is a carboxylic acid which when reacts with ethanol (alcohol) produces sweet smelling ester. The process in which the carboxylic acid reacts with alcohol, in the presence of a catalyst, to form an ester is called esterification.
The chemical equation for the above reaction is as follows: