When $H_2S$ is passed through a mixture containing $Cu^{2+}$,$Ni^{2+}$,and $Zn^{2+}$ in an acidic solution,which ion will precipitate?

Identify the metal $M$ and the precipitate $Z$ in the following reaction sequence:
$MSO_4$ $\xrightarrow{NH_4OH} \downarrow X \text{ (white)}$ $\xrightarrow{NH_4OH \text{ (excess)}} Y$ $\xrightarrow{H_2S} \downarrow Z$

The cation that will not be precipitated by $H_2S$ in the presence of $dil. \ HCl$ is

The only cations present in a slightly acidic solution are $Fe^{3+}$,$Zn^{2+}$,and $Cu^{2+}$. The reagent that when added in excess to this solution would identify and separate $Fe^{3+}$ in one step is

Which of the following gives a black precipitate when $H_2S$ gas is passed through its solution?

Assign $A, B, C, D$ from the given type of reaction.
$FeCl_3 + NH_3 \text{ (excess)} \longrightarrow Fe(OH)_3 \downarrow$