Most of us have classified strong and weak acids/bases as all or nothing; i.e., strong has to do with does it ionize 100%(or close to 100%) or not. If yes we say it is strong, if not we say it is weak. If you read much on the internet, especially about strong/weak bases you come up with good explanations on NaOH, RbOH, Ca(OH)2, etc as being strong. But when we come to Cu(OH)2, Al(OH)3, Fe(OH)2, Fe(OH)3, and others, the shift goes to "well these aren't very soluble so the OH^- isn't very large so these are weak bases". That is, the idea of ionization never enters the picture. Therefore, some texts classify acid/bases as soluble strong/weak acid/bases and insoluble bases and in that manner get around calling Fe(OH)2, Fe(OH)3, Al(OH)3 etc as strong or weak. They simply are insoluble bases. This may be more than you ever wanted to know about acids/bases but it's a little confusing even for those of us that's been in the field for years and more years.
So here are my answers and comments on each.
*hydroxides of group IIIA (13) metals
I think most will classify these as weak bases. For example, Al(OH)3, although quite insoluble, is not very ionic either but is it 100% ionized? How often do we talk about unionized Al(OH)3. Not often. In fact I might suggest never. Personally I think it should be classified as a strong base but I expect most will disagree with me.
*conjugate bases of strong acids
Strong acids have conjugate bases that are weak bases.
*hydroxides of group IA (1) metals
All of these are ionized 100% and are strong.
*hydroxides of transition metals
Most would call these weak because they are insoluble. But do they ionizae 100% or not?
*hydroxides of group IIA (2) metals
These are soluble and ionize 100% so they are strong bases. Usually Be(OH)2 is excluded from this list because it is (i) largely insoluble and (ii) has weak acidic properties so it is a weak base.
What kinds of compounds are typically strong bases? (More than one may apply.)
*hydroxides of group IIIA (13) metals
*conjugate bases of strong acids
*hydroxides of group IA (1) metals
*hydroxides of transition metals
*hydroxides of group IIA (2) metals
All I know about strong bases are that they dissociate completely in water, but I don't know how or why.
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Thank you so much for a detailed explanation! I understand partially what you're saying, and I'll clarify with my teacher as to how much I need to understand.
I think it is time that someone clarified the definition of strong/weak acids/bases and/or examples of those that are insoluble. Of course I could be mixed up; in that case, perhaps I could be clarified. :-)
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