Question #300fd

1 Answer
Apr 8, 2017

Because it ionizes completely in aqueous solution.


Sodium hydroxide is a strong base because it ionizes completely when dissolved in water, i.e. for every mole of sodium hydroxide that you dissolve you get #1# mole of hydroxide anions.

#"NaOH"_ ((aq)) -> "Na"_ ((aq))^(+) + "OH"_ ((aq))^(-)#

This means that sodium hydroxide solutions have a very high concentration of hydroxide anions, which, in turn, implies a very low concentration of hydronium cations, #"H"_3"O"^(+)#, i.e. a very high #"pH"#.

So, we consider sodium hydroxide a strong base because this compound is #100%# dissociated in aqueous solution, i.e. sodium hydroxide exists as ions when dissolved in water.