Review of 14A: Identifying AlCl3 as Acidic

[Vienna 1G]

Hello! I came across a salt compound in one of the textbook questions (6D.15b)), AlCl₃. I know this salt will act as an acid, because Al has a large positive charge and will enable water to lose a proton and become H3O+. However, is there a general rule for identifying whether a salt is an acid or a base? For example, are all metals with large positive charges going to act as an acidic salt? Or are group 1 and group 2 cations going to form acidic salts?

I haven't taken 14A in a couple quarters, and I don't remember the rules around salt acidity. I've heard that a strong acid + strong base = neutral salt, strong acid + weak base = acidic salt, weak acid + strong base = basic salt, weak acid + weak base = neutral salt. But how do I know the strength of the acids and bases the salt is made of? Is it necessary to memorize the lists of strong acids and strong bases, so I can identify the acidity of salts?

[Zoe 1I]

Here are some rules to use:
Cations

Neutral:
Group 1 or 2
Transition metals with charge +1

Acidic:
Transition metal w charge >+1
Conjugate acid of weak base

Anions

Neutral:
Conjugate base of strong acid

Basic:
Conjugate base of weak acid

[rin homma 2A]

Dr. Lavelle said in class that you didn't have to worry, because he would provide Kb or Ka in the problems. If you remember your 14A stuff, you could use it, but that the high Ka (and low pKa) would indicate that it was a strong acid.