Stanton D. answered 04/11/21
Tutor to Pique Your Sciences Interest
Hi Cole B.,
We shall assume you mean, the equilibrium expression for pyridine acting as a base? That would be the reaction C5H5N + H(+) = C5H5NH(+)
and the expression is K = [C5H5NH(+)] / ([C5H5N][H(+)]) . By the way, the value for the K here may depend on the solvent in which the protonation is taking place ------ but you knew that already, right?
in particular, the strength of an acid (such as C5H5NH(+)) may vary. Superacids, which may be millions of times more acidic than H3O(+), dump their protons when they hit water, so they aren't particularly corrosive any more. Likewise, with superbases (things much stronger than OH(-), such as CH3(-)).
But if you meant, "basic equilibrium expression" in the sense of "just your everyday, ordinary one", well, can't help you there.
--Cheers, --Mr. d.