$A$ solution containing a group $IV$ cation gives a precipitate on passing $H_2S$ gas. $A$ solution of this precipitate in dilute $HCl$ produces a white precipitate with $NaOH$ solution and a bluish-white precipitate with basic potassium ferrocyanide. The cation is:

The only cations present in a slightly acidic solution are $Fe^{3+}$,$Zn^{2+}$,and $Cu^{2+}$. The reagent that when added in excess to this solution would identify and separate $Fe^{3+}$ in one step is

$A$ metal nitrate reacts with $KI$ to give a black precipitate which on addition of excess of $KI$ converts into an orange-colored solution. The cation of the metal nitrate is

On saturating an aqueous solution of $Cu(II)$,$Pb(II)$,and $Zn(II)$ ions with $H_2S$,which of the following will precipitate?

Conc. $HNO_3$ is added before proceeding to test for group $III$ members. This is to

An inorganic compound $X$ on treatment with concentrated $H_{2}SO_{4}$ produces brown fumes and gives a dark brown ring with $FeSO_{4}$ in the presence of concentrated $H_{2}SO_{4}$. Also,compound $X$ gives a precipitate $Y$ when its solution in dilute $HCl$ is treated with $H_{2}S$ gas. The precipitate $Y$ on treatment with concentrated $HNO_{3}$ followed by excess of $NH_{4}OH$ further gives a deep blue coloured solution. Compound $X$ is: