Question

Distinguish between the following pair of compound using the test given within bracket.

Iron (II) sulphate and iron (III) sulphate (using ammonium hydroxide)

Answer 1

	Iron (II) sulphate	Iron (III) sulphate
1.	On adding ammonium hydroxide, a dirty green precipitate of iron(II) hydroxide, Fe(OH)2, is formed.	On adding ammonium hydroxide, a reddish-brown precipitate of iron(III) hydroxide, Fe(OH)3, is formed.
2.	The precipitate is insoluble in excess ammonium hydroxide and gradually turns brown on exposure to air.	The precipitate is insoluble in excess ammonium hydroxide.
3.	\[\ce{\underset{\text{(Light green solution)}}{FeSO4} + 2NH4OH ->\underset{\text{(Dirty green ppt.)}}{Fe(OH)2} + (NH4)2SO4}\]	\[\ce{\underset{\text{(Yellow solution)}}{FeCl3} + 3NH4OH ->\underset{\text{(Reddish brown ppt.)}}{Fe(OH)3} + NH4Cl}\]