chapter 15 sec 1 the concept of ph p. 499-510 1 modern chemistry chapter 15 acid-base titration and...
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Chapter 15 Sec 1 The Concept of pH p. 499-510
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Modern ChemistryChapter 15
Acid-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
Chapter 15 Sec 1 The Concept of pH p. 499-510
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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 25C: [H3O+] = [OH-] = 1.0 x 10-7
M
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Self Ionization of Waterp
.49
9
[OH-] = 1x10-
7M
[H3O+] = 1x10-
7M
BASE ACID ACID BASE
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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 25C
• This is the ionization constant for water.
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H3O+ and OH-
BASIC [H3O+] < [OH-]
NEUTRAL [H3O+] = [OH-]
ACIDIC [H3O+] > [OH-]
OH-
OH-
OH-
H3O+
H3O+
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 10–4 M solution of HNO3 has been prepared for a laboratory experiment.
a.Calculate the [H3O+] of this solution.
b.Calculate the [OH–].
a. 1.0 × 10−4 M H3O+ b. 1.0 × 10−10 M OH-
Chapter 15 Sec 1 The Concept of pH p. 499-510
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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 M;[OH−] 1.0 10−11 M
Chapter 15 Sec 1 The Concept of pH p. 499-510
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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 M;[OH−] 3.0 10−2 M
[H3O] 5.0 10−11 M;[OH−] 2.0 10−4 M
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The pH Scale• pH – the negative of the common log
of the hydronium ion concentration• Based on the hydrogen ion
concentration.• Pouvoir hydrogéne (french) :
hydrogen power• Scale of 0-14 • <7 Acidic
=7 Neutral>7Basic
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The pH Scale
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
pH = -log [H3O+]
Chapter 15 Sec 1 The Concept of pH p. 499-510
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Relationship of [H3O+] to [OH-] and pH
p.
50
9
Chapter 15 Sec 1 The Concept of pH p. 499-510
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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
What is the lowest that [H3O+] can be? 1 x 10 -14
pH=0
pH=14
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pH Scalep
. 5
03
Chapter 15 Sec 1 The Concept of pH p. 499-510
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The p
H S
cale
Chapter 15 Sec 1 The Concept of pH p. 499-510
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pH of Common Materialsp
. 5
04
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pH of Common Materialsp
. 5
12
Chapter 15 Sec 1 The Concept of pH p. 499-510
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Usi
ng Y
our
Calc
ula
tor
pH = 4 = -log [H3O+]
pH = -log [2.3x10-8]
[EE]
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Sample Problems p.505
What is the pH of a 1.0 x 10–3 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
Chapter 15 Sec 1 The Concept of pH p. 499-510
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Sample Problems p.506
What is the pH of a solution if the [H3O+] is 3.4 x 10–5 M?
4.47
Chapter 15 Sec 1 The Concept of pH p. 499-510
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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
Chapter 15 Sec 1 The Concept of pH p. 499-510
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Sample Problems p.507
Determine the hydronium ion concentration of an aqueous 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.What is the hydronium ion concentration of this solution?
2. The pH of a solution is determined to be 12.0.What is the hydronium ion concentration of this 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• <7 basic
=7 neutral>7 acidic
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pO
H a
nd H
ydro
xid
e
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[H3O+] for Strong & Weak AcidsFor Strong Acids
HCl H+ + Cl-
0.10M 0.10M 0.10MUse the mole ratio.
For Weak AcidsHF H+ + F-
0.10M <0.10M <0.10M Use the “I.C.E.” or use
equilibrium concentrations.
REVIEW
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Calculating [H3O+] [OH-]
pH = -log [H3O+]
Kw = 1.00 x 10-14 = [H3O+] [OH-]
Ka= [negative ion] [H3O+]
[acid molarity]
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Calculating [H3O+] [OH-]
[H3O+
].
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Weak Acid Problems
Assume that enough lactic acid, CH3CHOHCOOH, is dissolved in sour milk to give a solution concentration 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. HNO2+H2OH3O+ + 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
Chapter 15 Sec 1 The Concept of pH p. 499-510
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taci
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& N
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traliz
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Chapter 15 Sec 1 The Concept of pH p. 499-510
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Ch 15 Sec 1 Homework
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