Ph

Chapter 9 Acids and Bases Ionization of Water The pH Scale

LecturePLUS Timberlake

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Ionization of Water Occasionally, in water, a H+ is transferred between H2O molecules

..

..

..

H:O: +

:.O.:H

H:O:H +

.. H

H

water molecules

..

.. +

:O : H..

H hydronium hydroxide ion (+) ion (-) LecturePLUS Timberlake

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Pure Water is Neutral Pure water contains small, but equal amounts of ions: H3O+ and OH-

H2O + H2O H 3O +

OH-

H3O+

+

OH-

hydronium hydroxide ion ion

1 x 10-7 M 1 x 10-7 M LecturePLUS Timberlake

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Ion Product of Water Kw [ Kw

] = Molar concentration =

[ H3O+ ] [ OH- ]

=

[ 1 x 10-7 ][ 1 x 10-7 ]

=

1 x 10-14 LecturePLUS Timberlake

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Acids Increase H+ HCl (g) + H2O (l)

H3O+ (aq) + Cl- (aq)

More [H3O+] than water > 1 x 10-7M  As H3O+ increases, OH- decreases [H3O+] > [OH-] LecturePLUS Timberlake

H 3O +

OH5

Bases Increase the hydroxide ions (OH-) H2 O

NaOH (s) Na+(aq) + OH- (aq) More [OH-] than water, [OH-] > 1 x 10-7M  When OH- increases, H3O+ decreases [OH− ] > [H3O+] LecturePLUS Timberlake

H 3O +

OH6

Using Kw The [OH- ] of a solution is 1.0 x 10- 3 M. What is the [H3O+]? Kw

=

[H3O+ ] [OH- ]

[H3O+]

=

1.0 x 10-14

= 1.0 x 10-14

[OH-] [H3O+] =

1.0 x 10-14 1.0LecturePLUS x 10- 3Timberlake

= 1.0 x 10-11 M 7

Learning Check pH1 The [H3O+] of lemon juice is 1.0 x 10-3 M. What is the [OH-] of the solution? 1)

1.0 x 103 M

2)

1.0 x 10-11 M

3)

1.0 x 1011 M LecturePLUS Timberlake

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Solution pH1 The [H3O+] of lemon juice is 1.0 x 10- 3 M. What is the [OH-]? [OH- ] = 1.0 x 10 -14 1.0 x 10 - 3

=

LecturePLUS Timberlake

1.0 x 10-11 M

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Using the Calculator 1.0 x 10 -14 4.0 x 10-5 Enter 1.0 EE +/- 14 ÷

4.0 EE +/- 5

= 2.5 x 10 -10

LecturePLUS Timberlake

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Learning Check pH2 The [OH-] of a solution is 5 x 10 -5 M. What is the [H3O+ ] of the solution? 1)

2 x 10- 5 M

2)

1 x 1010 M

3)

2 x 10-10 M LecturePLUS Timberlake

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Solution pH2 The [OH-] of a water solution is 5 x 10-5 M. What is the [H3O+] in the solution? [ H3O+] = 1.0 x 10 -14 5 x 10- 5 On some calculators: 1.0 EE +/- 14

÷ 5 EE +/- 5 = 2 x 10 -10 M LecturePLUS Timberlake

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Learning Check pH3 A.The [OH-] when [H3O+ ] of 1 x 10- 4 M 1) 1 x 10-6 M 2) 1 x 10-8 M 3) 1 x 10-10 M B.The [H3O+] when [OH- ] of 5 x 10-9 M 1) 1 x 10- 6 M 2) 2 x 10- 6 M 3) 2 x 10-7 M LecturePLUS Timberlake

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Solution pH3 Kw = [H3O+ ][OH-] = 1.0 x 10 14 A. (3) [OH- ] =

1.0 x 10 -14 = 1.0 x 10 -10 1.0 x 10- 4

B. (2) [H3O+] =

1.0 x 10 -14 = 2 x 10 - 6 5 x 10- 9 LecturePLUS Timberlake

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pH  Indicates the acidity [H3O+] of the solution  pH = - log [H3O+]  From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)

LecturePLUS Timberlake

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pH In the expression for [H3O+]

1 x 10-exponent the exponent = pH

[H3O+] = 1 x 10-pH M LecturePLUS Timberlake

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pH Range 0

1

2

3 4 5

6

7 8 9 10 11 12 13 14 Basic

Acidic

Neutral

[H+]>[OH ] -

[H+] = [OH-] LecturePLUS Timberlake

[OH-]>[H ] +

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Some [H3O+] and pH [H3O+]

pH

1 x 10-5 M

5

1 x 10-9 M

9

1 x 10-11 M

11

LecturePLUS Timberlake

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pH of Some Common Acids gastric juice

1.0

lemon juice

2.3

vinegar

2.8

orange juice

3.5

coffee

5.0

milk

6.6 LecturePLUS Timberlake

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pH of Some Common Bases blood

7.4

tears

7.4

seawater

8.4

milk of magnesia

10.6

household ammonia

11.0

LecturePLUS Timberlake

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Learning Check pH4 A. The [H3O+] of tomato juice is 1 x 10-4 M. What is the pH of the solution? 1) - 4 2) 4 3) 8 B. The [OH-] of an ammonia solution is 1 x 10-3 M. What is the pH of the solution? 1)

3

2)

11 LecturePLUS Timberlake

3)

-11 21

Solution pH4 A. pH = - log [ 1 x 10-4] = -(- 4) = 4 B. [H3O+] = 1 x 10-11 pH = - log [ 1 x 10- 11] = -(- 11) = 11

LecturePLUS Timberlake

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Learning Check pH5 The pH of a soap is 10. What is the [H3O+] of the soap solution? 1) 1 x 10 - 4 M 2) 1 x 1010 M 3) 1 x 10 - 10 M LecturePLUS Timberlake

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Solution pH5 The pH of a soap is 10. What is the [H3O+] of the soap solution?

[H3O+]

= 1 x 10-pH M = 1 x 10-10 M LecturePLUS Timberlake

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pH on the Calculator [H3O+] is 4.5 x 10-6 M pH = 4.5 x EXP(or EE) 6+/- LOG +/= 5.35

LecturePLUS Timberlake

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Learning Check pH6 A soap solution has a [H3O+] = 2 x 10-8 M. What is the pH of the solution? 1) 8 2) 7.7 3) 6 LecturePLUS Timberlake

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Solution pH6 A soap solution has a [H3O+] = 2.0 x 10-8 M. What is the pH of the solution?

B) 2.0

EE

8

+/-

LOG +/- = 7.7

LecturePLUS Timberlake

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Learning Check pH7 Identify each solution as 1. acidic 2. basic

3. neutral

A. _____

HCl with a pH = 1.5

B. _____

Pancreatic fluid [H+] = 1 x 10-8 M

C. _____

Sprite soft drink pH = 3.0

D. _____

pH = 7.0

E. _____

[OH- ] = 3 x 10-10 M

F. _____

[H+ ] = 5 x 10-12 LecturePLUS Timberlake

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Solution pH7 Identify each solution as 1. acidic 2. basic

3. neutral

A. _1__

HCl with a pH = 1.5

B. _2__

Pancreatic fluid [H+] = 1 x 10-8 M

C. _1__

Sprite soft drink pH = 3.0

D. _3__

pH = 7.0

E. _1__

[OH-] = 3 x 10-10 M

F. _2__

[H+] = 5 x 10-12 LecturePLUS Timberlake

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Acid Rain Unpolluted rain has a pH of 5.6 Rain with a pH below 5.6 is “acid rain“ CO2 in the air forms carbonic acid CO2 + H2O

H2CO3

Adds to H+ of rain H2CO3

H+ (aq) + HCO3-(aq) LecturePLUS Timberlake

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Sources of Acid Rain Power stations Oil refineries Coal with high S content Car and truck emissions Bacterial decomposition, and lighting hitting N2 LecturePLUS Timberlake

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SO2

26 million tons in 1980

NO and NO2

22 million tons in 1980

Mt. St Helens (1980)

400,000 tons SO2

Reactions with oxygen in air form SO3 2SO2 + O2

2 SO3

Reactions with water in air form acids SO3 + H2O

H2SO4 sulfuric acid

NO + H2O

HNO2 nitrous acid

HNO2 + H2O

HNO nitric acid

LecturePLUS Timberlake 3

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Effects of Acid Rain Leaches Al from soil, which kills fish Fish kills in spring from runoff due to accumulation of large amounts of acid in snow

Dissolves waxy coatings that protect leaves from bacteria

Corrodes metals, textiles, paper and leather LecturePLUS Timberlake

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