Upon treatment with ammoniacal $H_2S$,the metal ion that precipitates as a sulfide is

Sodium nitroprusside when reacts with a solution of $Na_2S$,produces:

Which reagent is used in the qualitative analysis of Group $IV$ cations?

In the analysis of basic radicals,the group reagent $H_2S$ gas is generally used in which groups?

Nessler's reagent is

Identify the correct reactions and observations from the following:
$(1) \ NH_4^+ \xrightarrow[K_2HgI_4]{KOH} \text{ Brown ppt. (Nessler's reagent)}$
$(2) \ Ni^{2+} \xrightarrow{dmg/OH^-} \text{ Rosy red ppt.}$
$(3) \ FeCl_3(aq.) \xrightarrow{NH_4OH} \text{ Reddish brown ppt.}$
$(4) \ CuSO_4(aq.) \xrightarrow{\text{excess } NH_4OH} \text{ Deep blue solution}$