Question

Distinguish between the given pair of compounds using the test given within brackets:

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

Answer 1

On addition of ammonium hydroxide to iron sulphate (II), a dirty green precipitate of \[\ce{Fe(OH)2}\] is formed. On treating iron sulphate (III) solution with ammonium hydroxide, a reddish-brown precipitate of \[\ce{Fe(OH)2}\] is formed.

Answer 2

Iron (II) sulphate and iron (III) sulphate (using \[\ce{NH4OH}\])

Iron (II) sulphate (\[\ce{Fe2+}\] ion)

\[\ce{\underset{green}{FeSO4} + 2NH4OH -> \underset{dirty green ppt}{Fe(OH)2↓} +  \underset{colourless sol}{(NH4)2SO4}}\]

Iron (III) Salt (\[\ce{Fe^{3+}}\] ion)

\[\ce{Fe2(SO4)3 + 6NH4OH↓ -> \underset{reddish brown ppt}{2Fe(OH3)↓} + 3(NH4)2SO4}\]