Chapter 15 Sec 1 The Concept of pH p' 499510

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Modern ChemistryChapter 15Acid-Base Titration
and pH
Sections 1 2 Aqueous Solutions and the Concept
of pH Determining pH and Titrations
Chapter 15 Sec 1 The Concept of pH p. 499-510
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Aqueous Solutions and the Concept of pH
Chapter 15 Sec 1 The Concept of pH p. 499-510
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Chapter 15 Vocabulary

• Self Ionization
• pH
• pOH
• Acid-base indicator
• Transition interval
• Titration
• Equivalence Point
• Endpoint

• Standard Solution
• Primary Standard
• Standardization

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Self Ionization of Water

• Two water molecules produce a hydronium ion and a 
  hydroxide ion by transfer of a proton. 
• Water is a weak electrolyte. 
• H2O(l)  H2O(l) ? H3O(aq)  OH-(aq) 
• At 25?C H3O  OH-  1.0 x 10-7 M 

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Self Ionization of Water
ACID
BASE
ACID
BASE
OH- 1x10-7M
H3O 1x10-7M
p.499
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Ionization Constant for H2O

• H2O(l)  H2O(l) ? H3O(aq)  OH-(aq) 
• The Keq for water  Kw  H3O OH- 
• 1 
• Kw  H3O OH-  1.0 x 10-14 at 25?C 
• This is the ionization constant for water. 

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H3O and OH-
ACIDIC   H3O gt OH-  NEUTRAL H3O  OH
-  BASIC H3O lt OH-
H3O
OH-
OH-
H3O
OH-
H3O
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Calculating H3O OH-

• If H3O is known then use 
• 1.0 x 10-14  H3O  OH- 
• to get OH-. 
• This works for strong and weak acids.

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Concentrations Kw
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Sample Problems p.502

• A 1.0 x 104 M solution of HNO3 has been prepared
  for a laboratory experiment.
• Calculate the H3O of this solution.
• Calculate the OH.

a. 1.0 10-4 M H3O b. 1.0 10-10 M OH-
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Practice Problems p.502
1. Determine the hydronium and hydroxide ion
concentrations in a solution that is 1 10-4 M
HCl. 2. Determine the hydronium and hydroxide
ion concentrations in a solution that is 1.0
10-3 M HNO3.
H3O 1 10-4 M OH- 1 10-10 M
H3O 1.0 10-3 MOH- 1.0 10-11 M
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Practice Problems p.502
3. Determine the hydronium and hydroxide ion
concentrations in a solution that is 3.0 10-2 M
NaOH. 4. Determine the hydronium and hydroxide
ion concentrations in a solution that is 1.0
10-4 M Ca(OH)2.
H3O 3.3 10-13 MOH- 3.0 10-2 M
H3O 5.0 10-11 MOH- 2.0 10-4 M
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The pH Scale

• pH  the negative of the common log of the hydroni
  um ion concentration 
• Based on the hydrogen ion concentration. 
• Pouvoir hydrogéne (french)  hydrogen power 
• Scale of 0-14 
• lt7 Acidic7 Neutralgt7Basic 

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The pH Scale
pH -log H3O
log 1.0 x 10?  ?    What is the pH if H3O 1.0
 x 10-12?  log 1.0 x 10-12  -12  - log 1.0 x 10
-12  12 
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Relationship of H3O to OH- and pH
p. 509
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The pH Scale
pH -log H3O
If 1.00 x 10-14 H3O OH- what is the
highest that H3O can be?
1 x 10 0
pH0
What is the lowest that H3O can be?
1 x 10 -14
pH14
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pH Scale
p. 503
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pH of Common Materials
p. 504
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pH of Common Materials
p. 512
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pH 4 -log H3O ?????  pH -log 2.3x10-8
???????? EE ???? 
Using Your Calculator
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Sample Problems p.505
What is the pH of a 1.0 x 103 M NaOH solution?
11.00
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Practice Problems p.505
Determine the pH of the following solutions  a. 1
  10-3 M HCl b. 1.0  10-5 M HNO3 c. 1  10-4
M NaOH d. 1.0  10-2 M KOH
a. pH 3.0
b. pH 5.00
c. pH 10.0
d. pH 12.00
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Sample Problems p.506
What is the pH of a solution if the H3O is 3.4 
x 105 M?
4.47
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Practice Problems p.506
1. What is the pH of a solution if the H3O is
6.7 10-4 M? 2. What is the pH of a solution
with a hydronium ion concentration of 2.5 10-2
M? 3. Determine the pH of a 2.5 10-6 M HNO3
solution. 4. Determine the pH of a 2.0 10-2 M
Sr(OH)2 solution.
1. pH 3.17
2. pH 1.60
3. pH 5.60
4. pH 12.60
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Sample Problems p.507
Determine the hydronium ion concentration of an aq
ueous solution that has a pH of 4.0.
H3O 1 10-4 M
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Practice Problems p.508
1. The pH of a solution is determined to be 5.0.Wh
at is the hydronium ion concentration of this solu
tion? 2. The pH of a solution is determined to be
 12.0.What is the hydronium ion concentration of t
his solution?
H3O 1 10-5 M
H3O 1 10-12 M
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Practice Problems p.508
3. The pH of an aqueous solution is measured as 1.
50. Calculate the H3O and the OH-. 4. The pH
 of an aqueous solution is 3.67. Determine H3O.
H3O 3.2 10-2 M OH- 3.2 10-13 M
H3O 2.1 10-4 M
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pOH

• A scale based on the hydroxide ion concentration 
• 0-14 
• lt7 basic7 neutralgt7 acidic

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H3O for Strong Weak Acids
For Strong Acids  HCl ? H
Cl-  0.10M 0.10M 0.10M  Use the mole ra
tio.
REVIEW
For Weak Acids  HF ? H
F-   0.10M lt0.10M lt0.10M   Use the I.C.
E. or use equilibrium concentrations.
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Calculating H3O OH-
Ka negative ion H3O acid molarity
Ka
Kw
Kw 1.00 x 10-14 H3O OH-
pH -log H3O
pH
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Calculating H3O OH-
Ka
H3O .
pH
Kw
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Weak Acid Problems
Assume that enough lactic acid, CH3CHOHCOOH, 
is dissolved in sour milk to give a solution conce
ntration of 0.10 M lactic acid.
A pH meter show that the pH of the sour milk is 2.
43. Calculate the Ka for the equilibrium system.
CH3CHOHCOOH ? CH3CHOHCOO-  H
1.44 x 10-4
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Weak Acid Problems
When the HNO2 is 0.08M, the pH of the acid is 2.
4 Calculate the Ka for the nitrous acid.
HNO2H2O?H3O  NO2-
2.1 x 10-4
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Acid Base Strength
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Ch 15 Sec 1 Homework
Calculating H3O, OH-, Ka  pH  Worksheet
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Ch 15 Sec 1 Homework
Page 509  1-6
Chapter 15 Sec 1 The Concept of pH p. 499-510
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