Which of the following can be used instead of $NH_4Cl$ in the analysis of group $III$ radicals?

$A$ solution containing a group $IV$ cation gives a precipitate on passing $H_2S$ gas. $A$ solution of this precipitate in dilute $HCl$ produces a white precipitate with $NaOH$ solution and a bluish-white precipitate with basic potassium ferrocyanide. The cation is:

Three different samples of a salt solution give the following test results: One sample gives a white precipitate with ammonia solution. One sample gives a white precipitate with dilute $NaCl$ solution. One sample gives a black precipitate with $H_2S$. Identify the salt.

An aqueous solution contains the ions as $Hg_2^{2+}$,$Hg^{2+}$,$Pb^{2+}$,and $Cd^{2+}$. The addition of dilute $HCl$ $(6 \ N)$ precipitates:

$A$ metal nitrate reacts with $KI$ to give a black precipitate which on addition of excess of $KI$ converts into an orange-colored solution. The cation of the metal nitrate is

Which of the following sulfides is completely precipitated upon dilution of its acidic solution?