The pH Scale

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2

4.0 x 10-5

Enter 1.0 EE +/- 14  4.0 EE +/- 5

= 2.5 x 10 -10

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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

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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

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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

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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

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pH

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Indicates the acidity [H3O+] of the solution

pH = - log [H3O+]

From the French pouvoir hydrogene

(“hydrogen power” or power of

hydrogen)

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LecturePLUS Timberlake

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In the expression for [H3O+]

1 x 10-exponent

the exponent = pH

[H3O+] = 1 x 10-pH M

pH

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pH Range

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Neutral

[H+]>[OH-] [H+] = [OH-] [OH-]>[H+]

Acidic

Basic

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LecturePLUS Timberlake

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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

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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

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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