What is observed when iron(II) ions are treated with aqueous ammonia?

• A. White precipitate insoluble in excess.
• B. Green precipitate soluble in excess.
• C. Red-brown precipitate insoluble in excess.
• D. No reaction.

Answer: (A)

When iron(II) ions meet a base in ammonia, the solution becomes more alkaline and iron(II) hydroxide starts to form as a solid. This precipitate is the solid Fe(OH)2, which appears as a pale/white (or very light) solid and, crucially, does not dissolve when more ammonia is added. The ammonia isn’t strong enough to convert it into a soluble complex, so you still see a solid precipitate even in excess. Over time, if exposed to air, it can oxidize and change color, but the initial observation with excess ammonia is a precipitate that remains solid.