Among the following cations,the number of cations which will give characteristic precipitate in their identification tests with $K_4[Fe(CN)_6]$ is :
$Cu^{2+}, Fe^{3+}, Ba^{2+}, Ca^{2+}, NH_4^{+}, Mg^{2+}, Zn^{2+}$

Which of the following basic radicals will not be precipitated by $H_2S$ gas in the presence of $NH_3$?

Which of the following sulfides is yellow in color?

$A$ colorless aqueous solution contains nitrates of two metals,$X$ and $Y$. When it was added to an aqueous solution of $NaCl$,a white precipitate was formed. This precipitate was found to be partly soluble in hot water to give a residue $P$ and a solution $Q$. The residue $P$ was soluble in aqueous $NH_3$ and also in excess sodium thiosulfate. The hot solution $Q$ gave a yellow precipitate with $KI$. The metals $X$ and $Y$,respectively,are

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

The only cations present in a slightly acidic solution are $Fe^{3+}$,$Zn^{2+}$,and $Cu^{2+}$. The reagent that when added in excess to this solution would identify and separate $Fe^{3+}$ in one step is