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This is what I saw from Chemistry: The Central Science 13th ed. by Theodore brown, page 698. It stated that there are two types of weak bases: one is those with lone pairs of electron and the other is anions of weak acids, which means conjugate bases of weak acids. My question is, aren't conjugate bases of weak acids strong bases? Because weak acids are less readily to give off proton but it's conjugate base can accept proton easily.

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marked as duplicate by Jan, Todd Minehardt, M.A.R. ಠ_ಠ, Loong, bon Nov 25 '15 at 19:11

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Your understanding is correct - on a relative scale, the conjugate base of a weak acid is a strong base, and the conjugate base of a strong acid is a weak base. For example, hydroxide ion (conjugate base of water) is a stronger base than acetate ion (conjugate base of acetic acid) which is a stronger base than chloride ion (conjugate base of hydrochloric acid).

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  • $\begingroup$ If mine is correct, why does the book says that weak bases are anions of weak acids since conjugate bases of weak acids are strong bases. $\endgroup$ – Theresa Nov 25 '15 at 16:54
  • $\begingroup$ Maybe it is a typo. These kinds of errors sometimes occur. Unfortunately I do not have a copy of the book to look at. Or maybe the author was thinking non-rigorously about, say, acetate ion as an example - it is indeed a "weak" base (compared to some bases) and acetic acid is a "weak" acid (compared to some acids). Just not the same ones. $\endgroup$ – iad22agp Nov 25 '15 at 16:57
  • $\begingroup$ It's not a typo but problem with definition - if any base stronger than water would be called strong this primitive rule would be ok. $\endgroup$ – Mithoron Nov 25 '15 at 17:02
  • $\begingroup$ Theresa, could you please quote exactly what Brown's book states, or post a picture of the offending paragraph? $\endgroup$ – iad22agp Nov 25 '15 at 18:56

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