Based on Le Chatelier's principle, what would happen to a saturated solution of borax at equilibrium if we added more B4O5(OH)4 2- ions?
Borax would precipitate from the solution.
Le Châtelier’s Principle states that if you apply a stress to a system at equilibrium, the equilibrium will shift in the direction that will remove the stress.
The chemical equation for your equilibrium is
Na₂[B₄O₅(OH)₅]·8H₂O(s) ⇌ 2Na⁺(aq) + B₄O₅(OH)₄²⁻(aq) + 8H₂O(l)
If you add more B₄O₅(OH)₄²⁻ ions, you are adding a stress to the right hand side of the equilibrium. The system will respond in a way that will relieve the stress.
The system can relieve some of the stress by getting rid of some of the B₄O₅(OH)₄²⁻ ions.
The position of equilibrium will shift to the left.
Borax will precipitate from the solution.