$X_2S_n + H_2O \to X(OH)_n \downarrow + Y \uparrow (Gas) \xrightarrow{Pb(CH_3COO)_2} Z \downarrow (Black \ ppt.)$
Then $(X)$ cation can not be

What color does lead acetate give with $H_2S$?

$M^{n+}(aq.) + KI \to X\downarrow \text{ (ppt.)}$ $\xrightarrow{Excess KI} \text{ppt. remains insoluble in excess } KI \text{ solution. Then cation } M^{n+}(aq.) \text{ can be}$

$p$-Amino-$N,N$-dimethylaniline is added to a strongly acidic solution of $X$. The resulting solution is treated with a few drops of aqueous solution of $Y$ to yield blue coloration due to the formation of methylene blue. Treatment of the aqueous solution of $Y$ with the reagent potassium hexacyanoferrate$(II)$ leads to the formation of an intense blue precipitate. The precipitate dissolves on excess addition of the reagent. Similarly,treatment of the solution of $Y$ with the solution of potassium hexacyanoferrate$(III)$ leads to a brown coloration due to the formation of $Z$.
$1.$ The compound $X$ is
$(A)$ $NaNO_3$ $(B)$ $NaCl$ $(C)$ $Na_2SO_4$ $(D)$ $Na_2S$
$2.$ The compound $Y$ is
$(A)$ $MgCl_2$ $(B)$ $FeCl_2$ $(C)$ $FeCl_3$ $(D)$ $ZnCl_2$
$3.$ The compound $Z$ is
$(A)$ $Mg_2[Fe(CN)_6]$ $(B)$ $Fe[Fe(CN)_6]$
$(C)$ $Fe_4[Fe(CN)_6]_3$ $(D)$ $K_2Zn_3[Fe(CN)_6]_2$
Give the answer for questions $1, 2$ and $3$.

Which reagent is used to distinguish between silver and lead salts?

What precipitate is formed when $SnCl_2$ is added to $HgCl_2$?