When ${\mathrm{I}}_2$ is passed through KCl, KF, KBr :

Because ${\mathrm{I}}_2$ is the weakest oxidising agent, it cannot replace ${\mathrm{Br}}_2,{\mathrm{Cl}}_2,\text{ or }{\mathrm{F}}_2$in $\mathrm{KBr},\mathrm{KCl}$ or $\mathrm{KF}$  . Hence When ${\mathrm{I}}_2$  is passed through KCl, KF, KB no reaction occurs.