$A$ precipitate of ....... would be obtained on adding $HCl$ to a solution of $(Sb_2S_3)$ in yellow ammonium sulphide.

On treating a solid salt $A$ with dil. $H_2SO_4$ and warming,reddish-brown fumes of gas $B$ are evolved. Addition of $C$ to the salt solution of $A$ followed by freshly prepared starch solution and acidification with acetic acid produces a blue colour. $C$ may contain:

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

$Fe^{2+}$ ion can be distinguished from $Fe^{3+}$ ion by

Three different samples of a salt solution give the following test results: One sample gives a white precipitate with ammonia solution. One sample gives a white precipitate with dilute $NaCl$ solution. One sample gives a black precipitate with $H_2S$. Identify the salt.

What color does lead acetate give with $H_2S$?