Titration of a Weak Acid with a Strong Base

This series of animations give a molecular view of the reactions that occur in the titration of a weak acid with a strong base. Here we deal with the major species in solution only. At the start of the titration we have a solution of a weak acid in which the major species is HA(aq). In the solution there are also small amounts of A-(aq) and H3O+(aq) but they are not shown. The titration reaction is shown below.

HA(aq)+ OH-(aq)<------>A-(aq)+ H2O(l)
Note that until we reach the stoichiometric point, OH-(aq) is in deficit and is completely consumed. At the half-neutralization point, the major species are HA(aq) and A-(aq) and at the stoichiometric point, the major species is A-(aq). Because A- is a base, the pH is greater than 7 at the stoichiometric point.