Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Winga on October 03, 2004, 09:20:52 AM
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For this two complexes:
[Al(OH2)6]^3+ & [Fe(OH2)6]^3+
The Al^3+ one is moe acidic. Why?
I have found 2 answers:
1. The charge to size ratio of Al^3+ is higher so the charge-charge repulsion of this metal center and the acidic proton is also higher.
2. The Al^3+ has a higher polarizing power that it polarizes the O-H bond.
Which one is more suitable for explaining this case?
Is there any better explanation?
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Who cares, though I prefer the second.
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The difference in acidity is almost certainly due to the relative stabilities of other metal-hydroxy complelexes ie Al(OH)2 + is probably more stable than Fe(OH)2 + resulting in more protons being formed in the Al solutions