The colour of the precipitate produced by adding $NaOH$ solution to $HgCl_2$ is

The pair$(s)$ of ions where $BOTH$ the ions are precipitated upon passing $H_2S$ gas in the presence of dilute $HCl$,is(are):
$(A) Ba^{2+}, Zn^{2+}$
$(B) Bi^{3+}, Fe^{3+}$
$(C) Cu^{2+}, Pb^{2+}$
$(D) Hg^{2+}, Bi^{3+}$

Addition of $SnCl_2$ to $HgCl_2$ gives a precipitate of which color?

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

An aqueous solution of an inorganic salt on treatment with $HCl$ gives a white precipitate. This solution contains

Aqueous solution of $FeSO_4$ does not produce a precipitate with: