Which of the following is soluble in yellow ammonium sulphide?

When $H_2S$ gas is passed through a hot acidic aqueous solution containing $Al^{3+}$,$Cu^{2+}$,$Pb^{2+}$ and $Ni^{2+}$,a precipitate is formed,which consists of

Nessler's reagent is

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

Given below are certain cations. Using inorganic qualitative analysis,arrange them in increasing group number from $0$ to $VI$.
$A. Al^{3+}$ $B. Cu^{2+}$
$C. Ba^{2+}$ $D. Co^{2+}$
$E. Mg^{2+}$
Choose the correct answer from the options given below:

What is formed when calomel $(Hg_2Cl_2)$ reacts with $NH_4OH$?