What happens when ammonia is added to iron sulfate?

When ammonia (NH₃) is added to iron(II) sulfate (FeSO₄) solution, a green precipitate of iron(II) hydroxide [Fe(OH)₂] forms. Ammonium sulfate [(NH₄)₂SO₄] also forms in the solution.

Reaction Explanation

The reaction can be represented by the following chemical equation:

FeSO₄(aq) + 2NH₃(aq) + 2H₂O(l) → Fe(OH)₂(s) + (NH₄)₂SO₄(aq)

Here's a breakdown of what happens:

1. Ammonia acts as a base: Ammonia in water forms ammonium hydroxide (NH₄OH), which is a weak base.

2. Hydroxide ions are generated: The ammonium hydroxide dissociates slightly to produce hydroxide ions (OH^-).

3. Iron(II) hydroxide precipitates: The hydroxide ions react with the iron(II) ions (Fe²⁺) from the iron(II) sulfate to form iron(II) hydroxide [Fe(OH)₂], which is insoluble in water and thus precipitates out of the solution as a green solid. If oxygen is present, the precipitate can quickly oxidize to a brownish-orange iron(III) hydroxide.

4. Ammonium sulfate forms: The remaining ammonium ions (NH₄⁺) and sulfate ions (SO₄^2-) stay in solution, forming ammonium sulfate [(NH₄)₂SO₄].

In summary, the addition of ammonia to iron(II) sulfate solution results in the formation of a green precipitate of iron(II) hydroxide and ammonium sulfate in solution.