[grodskib]

There are a lot of standard answers to the reason why metal ions like Al and Zn are amphoteric.  Al is said to have a high charge density in that its small ionic radius and large positive charge causes the electrons that are "electrostatically" bonded to Al are more polarized, making the electrons behave more covalently.


If this is true than why isnt a hexaqua al ion more acidic than an iron (III)  hexaqua ion?
Iron (III) has a larger Ka.

How does this make Aluminum hydroxide act as a an acid while iron (III) cannot.

What is the mechanism that a aluminum hydroxide hydrated ion undergos to act as an acid.  Does the hydrated water lose a hyrogen ion due to the stabilized conjugate base structure of  the complex or does a hydroxide ion attack the positive Aluminum ion disloging a water , somewhat water and carbon dioxide.

Any clarity here would be helpful.
Thanks