Explanation:
The pKa value of acetic acid is determined experimentally by plotting pH titration curve.
The hydrogen ion, H+ concentration can be determined by performing a pH titration of a weak acid with a strong base like NaOH etc.
Starting from the dissociation equation for the acid,
HA(aq) + OH-(aq) --> H3O+(aq) + A−(aq)
we obtain for the point of half equivalence (where half of the acid has reacted with the base):
[A−] = [HA].
From the equilibrium equation
it therefore follows that
pKa = pH.
