Would a solution of Mg2+ ions have a higher or lower pH than a solution of Al3+ ions ?

Answer 1

Both Mg²⁺ and Al³⁺ are Lewis acids as they will accept a pair of electrons.

The acidity of the solution of the metal ion is related to its ability to attract a pair of electrons or to the charge on the metal ion. Thus, a solution of Mg²⁺ ions would have a higher pH (less acidic) than a similar solution of Al³⁺ ions.