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

When a salt is treated with sodium hydroxide solution,it gives gas $X$. On passing gas $X$ through reagent $Y$,a brown-coloured precipitate is formed. $X$ and $Y$ respectively,are

In the group $III$ radicals,in place of $NH_4Cl$,which of the following can be used?

In the group analysis of cations, $Ba^{2+}$ and $Ca^{2+}$ are precipitated respectively as

The colour of copper sulphide is

Which of the following pairs cannot be separated by passing $H_2S$ gas?