© University of South Carolina Board of Trustees

Calculate the pH in the titration of 100.0 mL of 0.200 M HCl with 0.400 M NaOH after

a) 0.00 mL strong acid problem pH = 0.7b) 25.00 mL strong acid problem pH = 1.1c) 50.00 mL water + spectators pH = 7.0d) 75.00 mL strong base problem pH =12.8

of base are added.

Calculating a Titration Curve:Strong Acid + Strong Base

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Titration of aStrong Acid with Strong Base

pH = 7.0Spectator Ions

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Chapt. 16More Acids and Bases

Sec. 4-5Titration:

Weak Acid + Strong Base ( or weak base + strong acid)

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Titration of aWeak Acid with Strong Base

pH > 7.0

Equivalence Point

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Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10-5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL c) 10.00 mL d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10−5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL c) 10.00 mL d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10−5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem c) 10.00 mL d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10−5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Weak Acid Titration Curve

ab

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10−5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10−5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL weak base problem d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10−5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL weak base problem pH = 8.95

d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Weak Acid Titration Curve

ab

c pH = 8.95

Equivalence Point

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10-5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL weak base problem pH = 8.95

d) 15.00 mL

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Chapt. 15Flashback

Sec. 7Mixtures of Acids (Bases)

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If an acid (base) is much weaker (Ka ~100 x smaller) than another acid (base) in the problem, ignore it.

What is the pH of a solution that is 0.100 M in HCl and 0.050 M in HF?

What is the pH of a solution that is 0.100 M in HOCl and 0.050 M in HF?

Mixtures of Acids (Bases)

strong acid

weak acid

Ka = 3.0x10−8 Ka = 3.5x10−4

pKa = 7.52 pKa = 3.46 (reverse)

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10-5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL weak base problem pH = 8.95

d) 15.00 mL strong base problem

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Calculate the pH in the titration of 25.00 mL of 0.200 M acetic acid (Ka = 1.8 x10-5) with 0.500 M NaOH after

a) 0.00 mL weak acid problem pH = 2.72

b) 5.00 mL buffer problem pH = 4.74

c) 10.00 mL weak base problem pH = 8.95

d) 15.00 mL strong base problem pH =12.8

of base are added.

Calculating a Titration Curve:Weak Acid + Strong Base

© University of South Carolina Board of Trustees

Titration of aWeak Acid With Strong Base

ab

c

d

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Chapt. 16

Sec. 6Indicators

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pH Indicators

acid solutionunknown concentration

strong base solution known concentration

indicator dye changes color

record volume of base

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pH Indicators• Weak acid/base conjugate pair

• Acid and base forms are different colors

• Small amount used. Little affect on pH.

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Color Changes Near pKIn

HIn + H2O In− + H3O+

Look at [In−]/[HIn] when

pH = pKa - 1 pH = pKapH = pKa + 1

10% colored50% colored90% colored

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Strong-Acid / Strong-Base Titration

Equivalence Point: pH and color change suddenly

color changeKa

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Color Change with 1 Drop

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Want pKa Indicator ~ pH of Equiv. Point

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pH Indicators• Weak acid/base conjugate pair

• Acid and base forms are different colors

• Small amount used. Little affect on pH.

© University of South Carolina Board of Trustees

Titration - Indicator Detection

Equivalence Point: pH and color change suddenly

color changeKa