1. Strong Acid/Strong BasepH 7
Water
Strong Acid
Equivalence Pt.
mL of base added

2. Weak Base/Strong Acid Weak Base pH Conjugate Acid <7
Equivalence Pt.
Strong Acid
mL of acid added

3. Weak Acid/Strong Base Strong Base pH Conjugate base >7 Weak Acid
Equivalence Pt.
mL of base added

4. Indicators: generally complex molecules that are themselves weak acids in which the acid and conjugate base form exhibit different colors in solution

5. If Ka for the acid form of an indicator is 1 x 10-9 and the indicator is dumped into an acid solution with a pH = 0, what form of the indicator would be noticed?

6. If Ka for the acid form of an indicator is 1 x 10-9 and the indicator is dumped into an acid solution with a pH = 0, at what pH would the base form of the indicator become visible if base was added to the acid to increase the pH?

7. If Ka for the acid form of an indicator is 1 x 10-9 and the indicator is dumped into an acid solution with a pH = 0, at what pH would the base form of the indicator become dominant if base was added to the acid to increase the pH?

9. Phenolphthalein changes in this range pH
Strong Acid/Strong Base
Phenolphthalein changes in this range pH
Bromthymol blue changes in this range 7
Note: Phenolphthalein would do a good job but bromthymol blue could be better.
Equivalence Pt.
mL of base added

10. Equivalence Pt.- When the titrant added is exactly enough to consume the substance being titrated.
AKA…the stoichiometric endpoint
Endpoint of the Titration – When the indicator undergoes a color change.
The Endpoint of the Titration best reveals the Equivalence Pt. when the indicator used has a pKa that is very similar to the pH at the equivalence pt.

11. Weak Acid/Strong Base pH
Alazarin Yellow R changes in this range.
11.1
Equivalence Pt.
mL of base added

12. Diprotic Indicators
H2Ind + H2O ↔ H3O+ + HInd-
(Yellow) (Orange)
HInd- + H2O ↔ H3O+ + Ind2-
(Orange) (Blue)
For H2Ind; pKa ≈ 6.4
For HInd-; pKa ≈ 11.7
@ pH = 0
Ka1 = = [HInd-] = 1
[H2Ind] ~1 million

13. Yellow Diprotic Indicators H2Ind + H2O ↔ H3O+ + HInd-
(Yellow) (Orange)
HInd- + H2O ↔ H3O+ + Ind2-
(Orange) (Blue)
For H2Ind; pKa ≈ 6.4
Yellow
For HInd-; pKa ≈ 11.7
@ pH = 0
Ka2 = = [Ind2-] = 1
[Hind-] ~1 trillion

14. Diprotic Indicators
H2Ind + H2O ↔ H3O+ + HInd-
(Yellow) (Orange)
HInd- + H2O ↔ H3O+ + Ind2-
(Orange) (Blue)
For H2Ind; pKa ≈ 6.4
For HInd-; pKa ≈ 11.7
@ pH = 8
Ka1 = = [HInd-] = ~ 100
[H2Ind]

15. Orange Diprotic Indicators H2Ind + H2O ↔ H3O+ + HInd-
(Yellow) (Orange)
HInd- + H2O ↔ H3O+ + Ind2-
(Orange) (Blue)
For H2Ind; pKa ≈ 6.4
Orange
For HInd-; pKa ≈ 11.7
@ pH = 8
Ka2 = = [Ind2-] = ~ 1
[HInd-]

16. Diprotic Indicators
H2Ind + H2O ↔ H3O+ + HInd-
(Yellow) (Orange)
HInd- + H2O ↔ H3O+ + Ind2-
(Orange) (Blue)
For H2Ind; pKa ≈ 6.4
For HInd-; pKa ≈ 11.7
@ pH = 13
Ka1 = = [HInd-] = ~107
[H2Ind]

17. Blue Diprotic Indicators H2Ind + H2O ↔ H3O+ + HInd- (Yellow) (Orange)
HInd- + H2O ↔ H3O+ + Ind2-
(Orange) (Blue)
For H2Ind; pKa ≈ 6.4
Blue
For HInd-; pKa ≈ 11.7
@ pH = 13
Ka2 = = [Ind2-] = ~100
[HInd-]