Yellow ammonium sulphide solution is a suitable reagent for the separation of

$Pb^{2+}$,$Cu^{2+}$,$Zn^{2+}$,and $Ni^{2+}$ ions are present in a given acidic solution. On passing hydrogen sulphide gas through this solution,the precipitate formed will contain:

The solution of $BiCl_{3}$ in dil. $HCl$ when diluted with water,forms a white precipitate which is:

Find the compound $A$ from the following reaction sequences:
$A$ $\xrightarrow{\text{aqua-regia}} B$ $\xrightarrow[(2) CH_3COOH]{(1) KNO_2 \mid NH_4OH} \text{yellow ppt}$

Which of the following ions gives a white precipitate when $HCl$ is added to its aqueous solution?

In the group analysis of cations, $Ba^{2+}$ and $Ca^{2+}$ are precipitated respectively as