Answer:
SO₄⁻² (aq) + Mg²⁺ (aq) ⇄ MgSO₄ (s) ↓
Precipitation reaction
Explanation:
Mg²⁻ is one of the metals at group 2 in the Perodic Table. This group is called, the alkaline earth metals.
To make precipitate the Mg²⁺ we can use a salt of sulfate, either flouride or phosphate. Those are three salts that can precipitate this metal.
We use sodium as cathion so, first of all we dissociate them:
Na₂SO₄ (aq) → 2Na⁺ (aq) + SO₄⁻² (aq)
NaF (aq) → Na⁺ (aq) + F⁻ (aq)
Na₃PO₄ (aq) → 3Na⁺ (aq) + PO₄⁻³ (aq)
In all cases, the reaction is of the precipitation type and is conditioned by the Kps, the solubility product constant. Let's bond the anions with Mg²⁺.
SO₄⁻² (aq) + Mg²⁺ (aq) ⇄ MgSO₄ (s) ↓ Kps
2F⁻ (aq) + Mg²⁺ (aq) ⇄ MgF₂ (s) ↓ Kps
2PO₄⁻³ (aq) + 3Mg²⁺ (aq) ⇄ Mg₃PO₄ (s) ↓ Kps
