Weak Base-Strong Acid Titrations

Concept #1: Whenever starting these titrations it is best to determine the equivalence volume of the titrant. 

Concept #2: Before the equivalence point has been reached we have the formation of a buffer. 

Concept #3: At the equivalence point we have no remaining weak base or strong acid, but instead an excess of conjugate acid or weak acid. 

Concept #4: Beyond the equivalence point we will have an excess of strong acid and conjugate acid or weak acid remaining. 

Weak Base-Strong Acid Titrations Calculations

Example #1: Pyridine (C6H5N) is a weak organic base with a Kb of 1.7x10-9. Suppose you were to titrate 25.0 mL of a 0.100 M aqueous solution of pyridine with a 0.100 M HCl solution. What is the pH at the equivalence point?

 

Example #2: In order to create a buffer 560.0 mL of 0.100 M potassium lactate is mix with 550.0 mL of 0.150 M lactic acid, HC3H5O3. What is the pH of the buffer solution after the addition of 700.0 mL of 0.100 M hydrobromic acid, HBr? The Ka of HC3H5O3 is 1.4 x 10-4.