Chapter 15 Sec 1 The Concept of pH p. 499-510 1 Modern Chemistry Chapter 15 Acid-Base Titration and pH Sections 1 & 2 Aqueous Solutions and the Concept.

Chapter 15 Sec 1 The Concept of pH p. 499-510

1

Modern ChemistryChapter 15

Acid-Base Titration and pH

Sections 1 & 2

Aqueous Solutions and the Concept of pH

Determining pH and Titrations


2

Aqueous Solutions and

the Concept of pH


3

Chapter 15 Vocabulary• Self Ionization• pH• pOH• Acid-base

indicator• Transition interval• Titration• Equivalence Point• Endpoint

• Standard Solution

• Primary Standard

• Standardization


4

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-


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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


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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+]


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Relationship of [H3O+] to [OH-] and pH

p.

50

9


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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


18

The p

H S

cale


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pH of Common Materialsp

. 5

04


20

pH of Common Materialsp

. 5

12


21

Usi

ng Y

our

Calc

ula

tor

pH = 4 = -log [H3O+]

pH = -log [2.3x10-8]

[EE]


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What is the pH of a 1.0 x 10–3 M NaOH solution?

11.00


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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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What is the pH of a solution if the [H3O+] is 3.4 x 10–5 M?

4.47


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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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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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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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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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pH = -log [H3O+]

Kw = 1.00 x 10-14 = [H3O+] [OH-]

Ka= [negative ion] [H3O+]

[acid molarity]


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[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


38 An

taci

ds

& N

eu

traliz

ati

on


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Ch 15 Sec 1 Homework

Page 509 # 1-6

Chapter 15 Sec 1 The Concept of pH p. 499-510 1 Modern Chemistry Chapter 15 Acid-Base Titration and pH Sections 1 & 2 Aqueous Solutions and the Concept.

Documents

o slide

o oh oh

concept of ph slide

ph scale ph

o oh neutral h

oh slide

oh basic h

oh acidic h