1. Acids
Lesson 18
Titration Curves

3. Titration Curves
 A titration curve is a graph of the pH versus the volume in a titration.
The equivalence point is the end of a titration where the stoichiometry of the reaction is exactly satisfied. moles H+ = moles OH-
The transition point is when an indicator changes color and [HInd] = [Ind-].

4. Choosing an Indicator
When you choose an indicator, you must pick one so that the transition point of the indicator matches the equivalence point of the titration.
Rule of thumb Salt Equivalence Point
Neutral 7
Basic 9
Acidic 5

5. is added to 1. Titration Curve: Strong Acid and Strong Base
HCl KOH → KCl HOH
neutral salt pH = 7
Bromothymol Blue- see page 7 data
50 mL of 0.10 M KOH is added to mL of 0.10 M HCl
is added to
We start here pH
Volume 0.10 M KOH added 14 7 25 50

6. 2. Titration Curve: Weak Acid and Strong Base
HCN KOH → KCN + H2O basic salt
Indicator pH = Phenolphthalein- see page 7 data
20 mL of 1.0 M HCN is added to mL of 1.0 M KOH
is added to pH
Volume 1.0 M HCN added 14 7 10 20

7. 3. Titration Curve: Strong Acid and Weak Base
HCl NH → NH4Cl acid salt
Indicator pH = Methyl Red- see page 7 data
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7 30 60

8. 6. Match the Curve with the ReactionpH
Volume .10 M KOH added 14 7 25 50
A. 3HCl Al(OH)3 → AlCl HOH
C. HCN KOH → KCN + HOH
B. HCl KOH → KCl + HOH

9. 6. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7 30 60
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl + HOH
C. HCN KOH → KCN + HOH

10. 6. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7 30 60
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH