Describe the electrophilic substitution reactions of chlorobenzene.

(N/A) Chlorobenzene undergoes electrophilic substitution reactions at the $o$- and $p$-positions due to the resonance effect of the chlorine atom,which increases electron density at these positions. The reactions are as follows:
$(i)$ Halogenation (Chlorination): Chlorobenzene reacts with $Cl_2$ in the presence of anhydrous $FeCl_3$ to form $o$-dichlorobenzene and $p$-dichlorobenzene.
$(ii)$ Nitration: Chlorobenzene reacts with concentrated $HNO_3$ and concentrated $H_2SO_4$ to form $1$-chloro-$4$-nitrobenzene (major) and $1$-chloro-$2$-nitrobenzene (minor).
$(iii)$ Sulphonation: Chlorobenzene reacts with concentrated $H_2SO_4$ upon heating to form $4$-chlorobenzenesulphonic acid (major) and $2$-chlorobenzenesulphonic acid (minor).