Prussian blue is due to the formation of

The solution of $II A$ group precipitate in dilute $HNO_3$ when treated with $NH_4OH$ becomes blue because of the presence of

Ferric ion forms a Prussian blue coloured precipitate due to the formation of:

The metal cation present in sodium nitroprusside is also present in:

In any ferric salt,on adding potassium ferrocyanide,a Prussian blue colour is obtained,which is:

Aqueous solution of a metallic nitrate $X$ reacts with $NH_4OH$ to form $Y$,which dissolves in excess $NH_4OH$. The resulting complex is reduced by acetaldehyde to deposit the metal. $X$ and $Y$,respectively,are