Acids
Lesson 20
Titration Curves
Titration Curves
A titration curve is a graph of the pH changes that occur during an
acid-base titration versus the volume of acid or base added.
There are three types of titration curves.
You need to be able to recognize each and then choose a suitable
indicator for that titration.
The equivalence point is the end of a titration where the stoichiometry
of the reaction is exactly satisfied, or moles H+ = moles OH-.
The transition point refers to when an indicator changes color and
[HInd] = [Ind-].
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.
When acid base titration is at the equivalence point, the acid has
neutralized the base leaving only a salt and water.
The pH of the equivalence point depends on type of salt.
Rule of thumb
If the salt is neutral the equivalence point
=
7
If the salt is basic the equivalence point
=
9
If the salt is acidic the equivalence point
=
5
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH →
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
+
HOH
1.
Titration Curve: Strong Acid and Strong Base
HCl +
Indicator
KOH → KCl
+
HOH
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
pH
14
7
0
0
25
Volume .10 M KOH added
50
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
pH
0.10 M HCl
14
7
0
0
25
Volume .10 M KOH added
50
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
pH
0.10 M HCl
14
7
Neutral Salt
0
0
25
Volume .10 M KOH added
50
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
pH
0.10 M HCl
14
0.10 M KOH
7
Neutral Salt
0
0
25
Volume .10 M KOH added
50
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
pH
14
7
0
0
25
Volume .10 M KOH added
50
1.
Titration Curve: Strong Acid and Strong Base
HCl +
KOH → KCl
Indicator
pH = 7
+
HOH
Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl
pH
14
7
0
0
25
Volume .10 M KOH added
50
2.
Titration Curve: Weak Acid and Strong Base
HCN + KOH →
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
+
HOH
2.
Titration Curve: Weak Acid and Strong Base
HCN +
Indicator
KOH → KCN
+
HOH
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
14
7
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
14
1.0 M KOH
7
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
14
1.0 M KOH
Basic Salt
7
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
14
1.0 M KOH
Basic Salt
7
1.0 M HCN
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
14
1.0 M KOH
Basic Salt
7
1.0 M HCN
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
14
7
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
Buffer Zone
14
7
0
0
10
Volume 1.0 M HCN added
20
2.
Titration Curve: Weak Acid and Strong Base
HCN +
KOH → KCN
Indicator
pH = 9
+
HOH
Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
pH
Buffer Zone
14
Weak Acid & Salt
are present
7
0
0
10
Volume 1.0 M HCN added
20
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
NH4+ +
Cl-
3.
Titration Curve: Strong Acid and Weak Base
HCl +
Indicator
NH3 →
NH4+ +
Cl-
3.
Titration Curve: Strong Acid and Weak Base
HCl +
Indicator
NH3 →
NH4+ +
pH = 5
Cl-
Methyl Red
3.
Titration Curve: Strong Acid and Weak Base
HCl +
Indicator
NH3 →
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
7
0
0
30
Volume 1.0 M NH3 added
60
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
7
1.0 M HCl
0
0
30
Volume 1.0 M NH3 added
60
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
7
1.0 M HCl
Acid Salt
0
0
30
Volume 1.0 M NH3 added
60
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
1.0 M NH3
7
1.0 M HCl
Acid Salt
0
0
30
Volume 1.0 M NH3 added
60
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
1.0 M NH3
7
1.0 M HCl
Acid Salt
0
0
30
Volume 1.0 M NH3 added
60
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
7
0
0
30
Volume 1.0 M NH3 added
60
3.
Titration Curve: Strong Acid and Weak Base
HCl +
NH3 →
Indicator
NH4+ +
pH = 5
Cl-
Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl
pH
14
7
Buffer Zone
Weak Base & Salt
0
0
30
Volume 1.0 M NH3 added
60
are present
4.
Match the Curve with the Reaction
pH
14
7
0
0
25
50
Volume .10 M KOH added
A.
3HCl + Al(OH)3 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH →
KCl
+
3HOH
+
HOH
+
HOH
4.
Match the Curve with the Reaction
pH
14
Bisect the verticle
pH = 7
7
0
0
25
50
Volume .10 M KOH added
A.
3HCl + Al(OH)3 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH →
KCl
+
3HOH
+
HOH
+
HOH
4.
Match the Curve with the Reaction
pH
14
Bisect the verticle
pH = 7
7
0
0
25
50
Volume .10 M KOH added
A.
3HCl + Al(OH)3 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH → KCl
+
3HOH
+
HOH
+
HOH
5.
Match the Curve with the Reaction
pH
14
7
0
0
30
Volume 1.0 M NH3 added
A.
3HCl + Al(OH)3 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH →
KCl
60
+
3HOH
+
HOH
+
HOH
5.
Match the Curve with the Reaction
pH
14
7
Bisect the verticle
pH = 5
0
0
30
Volume 1.0 M NH3 added
A.
3HCl + Al(OH)3 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH →
KCl
60
+
3HOH
+
HOH
+
HOH
6.
Match the Curve with the Reaction
pH
14
7
0
0
30
Volume 1.0 M NH3 added
A.
3HCl + Al(OH)3 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH →
KCl
60
+
3HOH
+
HOH
+
HOH
6.
Match the Curve with the Reaction
pH
14
Bisect the verticle
pH = 9
7
0
0
30
Volume 1.0 M NH3 added
A.
3HCl + Al(OH)2 → AlCl3
B.
HCl +
C.
HCN + KOH → KCN
KOH →
KCl
60
+
3HOH
+
HOH
+
HOH
6.
Match the Curve with the Reaction
pH
14
Bisect the verticle
pH = 9
7
0
0
30
Volume 1.0 M NH3 added
A.
3HCl + Al(OH)2 → AlCl3
B.
HCl +
C.
HCN +
KOH →
KCl
KOH → KCN
60
+
3HOH
+
HOH
+
HOH