#"Conjugate acid/conjugate base pairs"# are simply defined by proton exchange, i.e. addition or subtraction of #H^+#. As with any chemical reaction, charge and mass are conserved:
#underbrace(NH_4^+)_("conjugate acid") rarrunderbrace(NH_3)_("conjugate base") + H^+#
Ammonia is a good example for the #"conjugate acid/conjugate base relationship"# because it shows how acid/base chemistry can be extended beyond aqueous solution, and in liquid ammonia the following equilibrium operates:
#2NH_3(l) rightleftharpoons underbrace(NH_4^(+))_("conjugate acid of ammonia") + underbrace(NH_2^(-))_("conjugate base of ammonia")#
#K_"eq"# for this ammonolysis reaction is much smaller than for #K_"eq"# in the water solvent.
#NH_2^(-)# is the so-called #"amide ion"#; and is itself the conjugate acid of #NH^(2-)#, #"imide ion"#, which is itself the conjugate acid of #N^(3-)#, #"azide ion"#. These nitrogen bases are not encountered outside of liquid ammonia, a water-like solvent.
The take home message is that #"conjugate acid/conjugate base"# pairs are defined by proton exchange, i.e. #H^+#. All (?) you have to do is balance mass and charge.
In liquid #HF#, (an actual solvent), what is the conjugate acid and what is the conjugate base? Use the same procedure as before.
