$Pb(CH_3COO)_2$ gives a precipitate of which color with $H_2S$?

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

Three separate samples of a solution of a single salt gave these test results: one formed a white precipitate with excess ammonia solution,one formed a white precipitate with dilute $NaCl$ solution,and one formed a black precipitate with $H_2S$. The salt could be:

Sodium carbonate cannot be used in place of ammonium carbonate for the precipitation of the fifth group radicals because

Which of the following compounds changes the color of an aqueous $FeCl_3$ solution?

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