1. Review:
mL of 0.1 M barium hydroxide, Ba(OH)2, is added to 35 mL of 0.15 M hydrochloric acid, HCl. What is the pH of the resulting solution?

2. Review:
mL of carbonic acid, H2CO3, is titrated to the equivalence point with 24.3 mL of 0.1 M sodium hydroxide, NaOH. What was the original concentration of the acid?

3. What is a Polyprotic Acid?
In polyprotic acids, each ionizable proton dissociates in steps. Therefore in a titration, there are n equivalence points corresponding to each ionizable proton. For example in the titration of Na2CO3 with HCl, there are two equivalence points:
One for the formation of HCO3
One for the formation of H2CO3

4. Titration Animation

5. Polyprotic Acid Titrations:
Titration of H2C2O4 with NaOH
Polyprotic Acid Titrations:
Initial: H2C2O4 dissociating in water
Buffering zone 1: H2C2O4 + OH- 
1. Calculations rarely needed, concepts only!!!
Equivalence point 1: All H2C2O4 and OH-1 reacted, only HC2O4- left
2. Polyprotic Acids are titrated “step-wise”, one proton at a time.

6. Polyprotic Acid Titrations:
Buffering zone 2: HC2O4-1 begins to react with OH-1
Titration of H2C2O4 with NaOH
Polyprotic Acid Titrations:
Equivalence Point 2: All HC2O4-1 and OH-1 reacted, only C2O42- left
1. Calculations rarely needed, concepts only!!!
2. Polyprotic Acids are titrated “step-wise”, one proton at a time.

7. The initial sample of oxalic acid, before any titration Buffer Zone #1
Using the models provided on the handout, ID which represents the following points during the titration of H2C2O4.
The initial sample of oxalic acid, before any titration
Buffer Zone #1
Equivalence Point #1
Buffer Zone #2
Equivalence Point #2
Over-titration of the oxalic acid, too much base is added
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

8. The oxalic acid has been over-titrated
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

9. Buffer zone #1
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

10. Buffer zone #2
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

11. Equivalence Point #1
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

12. Equivalence Point #2
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

13. Initial sample of acid (no titration yet)
Spectator ions, water molecules, and very small amounts of H3O+ and OH- may be omitted

14. Acids and Bases