A weak base is the base that, upon dissolution in water, does non dissociate completely, so that a resulting aqueous sum contains only a small proportion of hydroxide ions together with the concerned basic radical, in addition to a large proportion of undissociated molecules of the base.
Calculate the pH and percentage protonation of a .20 M aqueous solution of pyridine, C5H5N. The Kb for C5H5N is 1.8 x 10−9.
First, write the proton transfer equilibrium:
The equilibrium table, with any concentrations in moles per liter, is
This means .0095% of the pyridine is in the protonated make of C5H5NH+.