$A$ black sulphide is formed by the action of $H_2S$ on

Which compound gives a black color with $NH_4OH$?

The reagent used for the identification of $Ni^{2+}$ ions is .....

Choose an incorrect match of the colour of compounds.

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

$A$ 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: