In the scheme given below, X and Y , respectively, are Metal halide...

The metal halide can be manganese dichloride. It gives white precipitate of manganese hydroxide.

${MnCl}_{2}\overset{aq . NaOH}{\to}\mathop{Mn{\left(OH\right)}_{2}}_{\left(P\right)} + \mathop{NaCl}_{\left(Q\right)}$

The white precipitate manganese hydroxide on reaction with lead dioxide and concentrated sulphuric acid gives purple coloured solution permanganate.

$Mn{\left(OH\right)}_{2}\mathop{\to}_{Conc . {H}_{2}{SO}_{4}, heat}^{{PbO}_{2}\left(excess\right)}{MnO}_{4}^{-}\left(purplesolution\right)$

The sodium chloride gives ${Cl}_{2}$ on reaction with $MnO{\left(OH\right)}_{2}, conc . {H}_{2}{SO}_{4}$. The chlorine formed can oxidise iodide to iodine which gives blue colouration with starch paper.