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?
Review of 14A: Identifying AlCl3 as Acidic
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Re: Review of 14A: Identifying AlCl3 as Acidic
Postby Zoe 1I » Mon Jan 29, 2024 4:44 pm
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
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
Last edited by Zoe 1I on Mon Jan 29, 2024 4:50 pm, edited 1 time in total.
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Re: Review of 14A: Identifying AlCl3 as Acidic
Postby rin homma 2A » Mon Jan 29, 2024 4:46 pm
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.
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