5. -5 M

6. Review:
50 mL of 0.1 M carbonic acid, H2CO3, with an initial pH of 3.5, is titrated with 0.2 M lithium hydroxide, LiOH. What volume of LiOH would be required to reach the first equivalence point? What additional volume would be required to reach the second equivalence point?

7. Objectives:
Learn how to properly choose an indicator for a given titration
Differentiate between the equivalence point and the end-point of a titration
Analyze titration curves for reverse titrations

8. Choosing the correct indicator:
Remember the role of an indicator?
It must change the color of the solution as close to the equivalence point as possible!!!

9. Choosing the correct indicator:
1. What indicator should be used for the titration of phenol with sodium hydroxide?
(pH at equivalence
point is 11.2)
2. What indicator should be
used for the titration of a
strong acid with a strong
base?

10. Choosing the correct indicator:
Remember the role of an indicator?
It must change the color of the solution as close to the equivalence point as possible!!!
The point in a titration when the indicator changes color is known as the end-point
The end-point is close to the equivalence point, but only an approximation

11. Reverse Titrations Normally, base is added to acid …
NaOH
and if the pH in the flask is monitored, titration curves look like this …
HCl

12. Reverse Titrations Acid can also be added to a base …
HCl
and if the pH in the flask is monitored, titration curves look like this …
NaOH

14. Reverse Polyprotic Titrations:
A chemical reaction occurs when M HCl is added dropwise to 30. mL of M Na3PO4. The sodium phosphate solution has an initial pH of 9.30, which decreases as HCl is added.
a. Write the 3 net ionic equations for the formation of the major species.

15. Reverse Polyprotic Titrations:
A chemical reaction occurs when M HCl is added dropwise to 30. mL of M Na3PO4. The sodium phosphate solution has an initial pH of 9.30, which decreases as HCl is added.
b. Sketch a graph using the axis provided, showing the shape of the titration curve that results when HCl is added from a burette to the Na3PO Exact pH values DO NOT need to be calculated, but volumes of titrant added should be calculated and represented accurately.