The ammonium cation,
This is essentially a neutralization reaction that takes place between a weak acid, the ammonium ion, and a strong base, sodium hydroxide.
The balanced chemical equation that describes the reaction looks like this
#"NH"_ (4(aq))^(+) + "OH"_ ((aq))^(-) -> "NH"_ (3(g)) uarr + "H"_ 2 "O"_ ((l))#
Because ammonia gas is given off, this reaction is used as a confirmatory test for the presence of the ammonium cations.