Strong bases like strong acids dissociate 100% in water. Strong bases are not themselves proton acceptors. They form OH- which is a proton acceptor. As such all the strong bases are ionic compounds where OH- is one of the ions. Such compounds are called hydroxides. Not all hydroxides are strong bases since not all hydroxides are highly soluble.
Strong bases are then hydroxides for which this equilibrium constant for the solubility is assumed to be 100%. For example KOH is a strong base, thus we assume this reaction goes to completion
\[\rm{KOH(s) \rightleftharpoons K^+(aq) + OH^-(aq)}\]
You need to memorize the list of strong bases (names and formulas)
Lithium hydroxide - LiOH
Sodium hydroxide - NaOH
Potassium hydroxide - KOH
Rubidium hydroxide - RbOH
Cesium hydroxide - CsOH
Calcium hydroxide - Ca(OH)2
Strontium hydroxide - Sr(OH)2
Barium hydroxide - Ba(OH)2
Note: These are all hydroxides of the group 1 metals and the group 2 metals starting at Ca and below. The others like Mg(OH)2 are not soluble (they have small Ksp's and thus are not strong bases).
Which of the following is not a strong base?
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