Find the number of compounds having zero dipole moment.

${\mathrm{PF}}_2{\mathrm{Cl}}_3,{\mathrm{PFCl}}_4,{\mathrm{PF}}_3{\mathrm{Cl}}_2,{\mathrm{H}}_2{\mathrm{O}}_2,{\mathrm{ClF}}_3,{\mathrm{SF}}_4,{\mathrm{CH}}_2{\mathrm{Cl}}_{2,}{\mathrm{F}}_2{\mathrm{O}}_2$ 1, 4-Dicyanobenzepe, p-Dichlorobenzene

${\mathrm{C}}_6{\mathrm{H}}_6\stackrel{{\mathrm{Cl}}_2,\mathrm{Fe}}{⟶}{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{Cl}\stackrel{{\mathrm{Cl}}_2}{\to }{\mathrm{O}}^{-}$ and p− dichlorobenzene

The result of the first reaction is chlorobenzene, and because the Cl group is ortho- and para-directing, the product is ortho- and para-dichlorobenzene.

Chlorination of chlorobenzene is the next step.