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

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:

Which of the following does not give a precipitate with $CrO_4^{2-}$?

Passing $H_2S$ gas into a mixture of $Mn^{2+}$,$Ni^{2+}$,$Cu^{2+}$ and $Hg^{2+}$ ions in an acidified aqueous solution precipitates

In the fifth group of qualitative analysis,$(NH_4)_2CO_3$ is added to precipitate out the carbonates. We do not add $Na_2CO_3$ because

Match List-$I$ with List-$II$ and select the correct answer using the codes given below.

List-$I$ (Ion involved)	List-$II$ (Agent)
$(i) \, Ni^{2+}$	$(A).$ Sodium thiosulphate
$(ii) \, Ag^{+}$	$(B).$ Sodium nitroprusside
$(iii) \, Cu^{2+}$	$(C).$ Ammonia
$(iv) \, S^{2-}$	$(D).$ Dimethylglyoxime