Reagents used for the qualitative estimation of $Ni^{+2}$ and $Cu^{+2}$ respectively are:

Aqueous solution of which of the following cation gives a precipitate with potash alum?

Which of the following ions forms a colored carbonate precipitate?

The group reagent for the precipitation of group $II$ basic radicals in qualitative analysis is:

In the wet tests for detection of various cations by precipitation,$Ba^{2+}$ cations are detected by obtaining a precipitate of

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: