What are the units of base dissociation constant Kb ?
Equilibrium constants, and acid/base dissociation constants fall under this umbrella, are usually regarded as dimensionless....
Of course for the reaction:
we would write the equilibrium constant as,
Here, CLEARLY, the units of concentration cancel to give
However, sometimes, we encounter an equilibrium rxn where the units do not cancel out, and in these circumstances we would strictly use DIMENSIONLESS standard state activities, where the concentration is expressed as an activity relative to a standard.
So thus, for the association of say,