Explain the given reactions with examples:
(a) Combustion reaction
(b) Oxidation reaction
(c ) Substitution reaction

Explanation

(a) Combustion reaction: Carbon compounds burns in oxygen to produce carbon dioxide alongwith release of large amount of heat and light.
`CH_(4)+2O_(2) to CO_(2)+2H_(2)O+` Heat and light
(b) Oxidation reaction: Ethanol is oxidised to ethanoic acid in the presence of alkaline `KMnO_(4)` (oxidising agent) on heating.
`CH_(3)CH_(2)OH underset("Heat") overset("Alk. "KMnO_(4))to CH_(3)COOH`
(c ) Substitution reaction: In the presence of sunlight, chlorine replaces the hydrogen atom of hydrocarbons.
`CH_(4)+Cl_(2) overset(hv) to CH_(3)Cl+HCl`