Acidity of metal aqua ions
Acidity of metal aqua ions
Formula
[M(H₂O)₆]ⁿ⁺ + H₂O ⇌ [M(H₂O)₅(OH)]⁽ⁿ⁻¹⁾⁺ + H₃O⁺
Real World
Aluminium chloride solutions used in antiperspirants are noticeably acidic on skin — the high charge density of Al³⁺ polarises coordinated water molecules enough to release H⁺ ions.
Exam Focus
Link acidity to charge density — higher charge and smaller ionic radius means greater polarisation of O–H bonds in coordinated water.
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