When $H_2S$ gas is passed through an $HCl$ solution containing $CuCl_2, HgCl_2, BiCl_3$,and $CoCl_2$,which of the following will not precipitate?

In which of the following is $NH_{3}$ not used?

Salt $X$ is:
$X \text{ (Colourless salt)}$ $\xrightarrow[\Delta]{NaOH} Y$ $\xrightarrow{HCl} \text{White fumes}$
$X \text{ (Colourless salt)}$ $\xrightarrow{CaCl_2} Z \text{ (White ppts.)}$ $\xrightarrow{KMnO_4} \text{Colourless solution}$

Which of the following reagents is commonly used to detect the presence of sulfide ions?

$A$ $0.3 \, M$ $HCl$ solution contains the following ions: $Hg^{2+}, Cd^{2+}, Sr^{2+}, Fe^{2+}, Cu^{2+}$. The addition of $H_2S$ to the above solution will precipitate which of the following?

Among $Fe^{3+}$, $Pb^{2+}$, $Cu^{2+}$, and $Mn^{2+}$, identify the one that gets precipitated out while passing $H_2S$ gas in the presence of $NH_4OH$ as a group reagent. The highest possible oxidation state of the corresponding metal is: