1. Chapter 16 Acids and Bases
Ionization of Water
The pH Scale
7-4

2. Measuring pH Why measure pH?
Everything from swimming pools, soil conditions for plants, medical diagnosis, soaps and shampoos, etc.
Sometimes we can use indicators, other times we might need a pH meter

4. pH of Some Common Acids gastric juice 1.0 lemon juice 2.3 vinegar 2.8
orange juice 3.5
coffee
milk

5. pH of Some Common Bases blood 7.4 tears 7.4 seawater 8.4
milk of magnesia 10.6
household ammonia 11.0

6. Calculating pH, pOH Relationship between pH and pOH
pH = -log10 [H3O+]
pOH = -log10 [OH-]
Relationship between pH and pOH
pH + pOH = 14
Finding [H3O+], [OH-] from pH, pOH
[H3O+] = 10-pH
[OH-] = 10-pOH

7. pH pOH [H+] [OH-] In pure water, [H3O+] = [OH-] = 1  10 –7
Kw = 1  10 –14
pH + pOH = 14 pH
pOH
pH = -log[H+]
pOH = -log[OH-]
[H+]
[OH-]
[H+][OH-] = 1.0  10-14

8. pH + pOH = 14

9. Ionization of Water . . . . . . . . H H H . . . . . . . .
Occasionally, in water, a H+ is transferred between H2O molecules
H:O: :O:H H:O:H :O:H-
H H H
water molecules hydronium hydroxide ion (+) ion (-)

10. Pure Water is Neutral H2O + H2O H3O+ + OH- H3O+ OH-
Pure water contains small, but equal amounts of ions: H3O+ and OH-
H2O + H2O H3O OH-
hydronium hydroxide ion ion
1 x 10-7 M 1 x 10-7 M
H3O+
OH-

11. Ion Product of Water Kw [ ] = Molar concentration
Kw = [ H3O+ ] [ OH- ]
= [ 1 x ][ 1 x 10-7 ]
= x 10-14

12. 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-]

13. Bases Increase the hydroxide ions (OH-) H2O
NaOH (s) Na+(aq) OH- (aq)
More [OH-] than water, [OH-] > 1 x 10-7M
When OH- increases, H3O+ decreases
[OH] > [H3O+]

14. Using Kw
The [OH- ] of a solution is 1.0 x M. What is the [H3O+]?
Kw = [H3O+ ] [OH- ] = x 10-14
[H3O+] = 1.0 x 10-14
[OH-]
[H3O+] = x = 1.0 x M
1.0 x 10- 3

15. Learning Check pH Kw = [H3O+ ] [OH- ] = 1.0 x 10-14
The [H3O+] of lemon juice is 3.0 x 10-3 M. What is the [OH-] of the solution?
Kw = [H3O+ ] [OH- ] = x 10-14
[OH- ] = 1.0 x 10-14
[H3O+]
[OH- ] = x = 3.3 x M
3.0 x 10- 3

16. pH The [H3O+] of lemon juice is 9.0 x 10- 4 M. What is the [OH-]?
[OH- ] = x = 1.1 x M
9.0 x

17. The [H3O+] is 4.0 x 10- 5 M. What is the [OH-]?
Enter 1.0 EE +/  EE +/- 5
= 2.5 x

18. Solution pH B.The [H3O+] when [OH- ] of 5 x 10-9 M
Kw = [H3O+ ][OH-] = 1.0 x 10 14
[H3O+] = x = 2 x
5 x 10- 9

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

20. pH [H3O+] = 1 x 10-pH M In the expression for [H3O+] 1 x 10-exponent
the exponent = pH
[H3O+] = 1 x 10-pH M

21. pH Range [H+]>[OH-] [H+] = [OH-] [OH-]>[H+]
Neutral
[H+]>[OH-] [H+] = [OH-] [OH-]>[H+]
Acidic
Basic

22. pH A. The [H3O+] of tomato juice is 1 x 10-4 M.
What is the pH of the solution?
answer: 4
pH = - log [ 1 x 10-4] = -(- 4) = 4

23. pH B. The [OH-] of an ammonia solution is
1 x 10-3 M. What is the pH of the solution?
Answer: 11
[H3O+] = 1 x 10-11
pH = - log [ 1 x ] = -(- 11) = 11

24. Some [H3O+] and pH
[H3O+] pH
1 x 10-5 M
1 x 10-9 M
1 x M

25. Solution pH [H3O+] = 1 x 10-pH M = 1 x 10-10 M
The pH of a soap is 10. What is the [H3O+] of the soap solution?
[H3O+] = 1 x 10-pH M
= 1 x M

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

27. Learning Check pH
A soap solution has a [H3O+] = 2 x 10-8 M. What is the pH of the solution?

28. pH
A soap solution has a [H3O+] = 2.0 x 10-8 M. What is the pH of the solution?
EE /- LOG +/- = 7.7

29. Learning Check 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 M
F. _____ [H+ ] = 5 x 10-12 1 2 1 3 1 2

30. What is the [H3O+ ] or [OH- ] in each of the following solutions, also state if the solution is neutral, acidic, or basic.
a. 1  M OH-
b. 1  M OH-
c M H+
1.0 x 10-9 M
1.0 x 10-7 M
1.0 x M