titration curves

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 + KOH → KCl + HOH

Indicator

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 Bromothymol Blue

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 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 + HOH

Indicator pH = 7 Bromothymol Blue

50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH

Volume .10 M KOH added

14

7

0

0 25 50

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 Bromothymol Blue

50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH

Volume .10 M KOH added

14

7

0

0.10 M HCl

0 25 50

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 Bromothymol Blue

50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH

Volume .10 M KOH added

14

7

0

0.10 M HCl

0 25 50

Neutral Salt

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 Bromothymol Blue

50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH

Volume .10 M KOH added

14

7

0

0.10 M HCl

0 25 50

Neutral Salt

0.10 M KOH

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 Bromothymol Blue

50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl

pH

Volume .10 M KOH added

14

7

0

0 25 50

1. Titration Curve: Strong Acid and Strong Base 

HCl + KOH → KCl + HOH

Indicator pH = 7 Bromothymol Blue

50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl

pH

Volume .10 M KOH added

14

7

0

0 25 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 + KOH → KCN + HOH

Indicator

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 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 + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

0 10 20

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

1.0 M KOH

0 10 20

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

1.0 M KOH Basic Salt

0 10 20

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

1.0 M KOH Basic Salt

1.0 M HCN0 10 20

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

1.0 M KOH Basic Salt

1.0 M HCN0 10 20

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

0 10 20

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

0 10 20

Buffer Zone

2. Titration Curve: Weak Acid and Strong Base

HCN + KOH → KCN + HOH

Indicator pH = 9 Phenolphthalein

20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

pH

Volume 1.0 M HCN added

14

7

0

0 10 20

Buffer Zone

Weak Acid & Salt

are present

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 + NH3 → NH4+ + Cl-

Indicator

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 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 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

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

0

0 30 60

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

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

0

1.0 M HCl

0 30 60

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

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

0

1.0 M HCl Acid Salt

0 30 60

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

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

0

1.0 M HCl Acid Salt

0 30 60

1.0 M NH3

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl

1.0 M HCl Acid Salt

1.0 M NH3

pH

Volume 1.0 M NH3 added

14

7

0

0 30 60

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

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

0

0 30 60

3. Titration Curve: Strong Acid and Weak Base 

HCl + NH3 → NH4+ + Cl-

Indicator pH = 5 Methyl Red

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

0

0 30 60

Buffer Zone

Weak Base & Salt

are present

pH

Volume .10 M KOH added

14

7

0

0 25 50

4. Match the Curve with the Reaction

A. 3HCl + Al(OH)3 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

pH

Volume .10 M KOH added

14

7

0

0 25 50

A. 3HCl + Al(OH)3 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

Bisect the verticlepH = 7

4. Match the Curve with the Reaction

pH

Volume .10 M KOH added

14

7

0

0 25 50

A. 3HCl + Al(OH)3 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

Bisect the verticlepH = 7

4. Match the Curve with the Reaction

A. 3HCl + Al(OH)3 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

0 30 60

pH

Volume 1.0 M NH3 added

14

7

0

5. Match the Curve with the Reaction

A. 3HCl + Al(OH)3 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

pH

Volume 1.0 M NH3 added

14

7

0

0 30 60

Bisect the verticlepH = 5

5. Match the Curve with the Reaction

A. 3HCl + Al(OH)3 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

pH

Volume 1.0 M NH3 added

14

7

0

0 30 60

6. Match the Curve with the Reaction

A. 3HCl + Al(OH)2 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

pH

Volume 1.0 M NH3 added

14

7

0

0 30 60

Bisect the verticlepH = 9

6. Match the Curve with the Reaction

A. 3HCl + Al(OH)2 → AlCl3 + 3HOH

B. HCl + KOH → KCl + HOH

C. HCN + KOH → KCN + HOH

pH

Volume 1.0 M NH3 added

14

7

0

0 30 60

Bisect the verticlepH = 9

6. Match the Curve with the Reaction