So we’ve heard of Ka/pKa, the acid dissociation constant – but what is there for bases? There is such a thing as a base dissociation constant Kb but more commonly the reverse of Ka is used.
A base would normally be indicated by a high pKa – meaning there is very little dissociated H+. Kb is simply the opposite as shown below.
So if we were to look at Ammonia (NH3):
But…seeing as we aren’t using Kb/pKb we simply need to rearrange our base dissociation formula to fit into Ka/pKa:
From this you may notice it’s the other way round for the Ka for acids, as there the top line holds the base NH3 while in acids the acid is found on the bottom line (eg HCl).
Acid Base Reactions – and Equilibrium
Acid base reactions have an equilibrium, and to calculate it we simply combine the Ka of the acids with the Ka of the bases.
Consider the reaction between HCl and NaOH, producing NaCl and H2O. Their Ka equations would be as follows:…