1. Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2

2. Chemistry FIFTH EDITION Chapter 14 Acids and Bases
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2

3. Percent Dissociation (Ionization)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

4. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Let’s Do
Problem 63
Note:
For solutions of any weak acid HA,
[H+] decreases as [HA]0 decreases;
BUT
The Percent Dissociation increases
as [HA]0 decreases.
For a given weak acid, the percent dissociation
Increases as the acid becomes more dilute.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

5. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Figure The Effect of Dilution on the Percent Dissociation and (H+) of a Weak Acid Solution
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

6. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Calculating Ka from
Percent Dissociation of a Weak Acid
See Sample Exercise 14.11
page 643
Let’s Do Problem #65
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

7. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Section Bases
Arrhenius Base:
Substance that produces OH- ions in aqueous solution.
Bronsted-Lowry Base:
A proton acceptor
Basic Solution: pH > 7
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

8. Section Bases
“Strong” and “weak” are used in the same sense for bases as for acids.
strong = complete dissociation (hydroxide ion supplied to solution)
NaOH(s)  Na+(aq) + OH(aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

9. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Strong Bases
Group 1A Hydroxides
NaOH
KOH
LiOH
RbOH
CsOH
Group 2A Hydroxides
Ca(OH)2
Ba(OH)2
Sr(OH)2
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

10. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Strong Bases
Group 1A Hydroxides
NaOH
KOH
LiOH  very expensive
RbOH  very expensive
CsOH  very expensive
Group 2A Hydroxides
Ca(OH)2
Ba(OH)2
Sr(OH)2
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

11. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Important & Interesting Information
about Bases
READ Section 14.6!
Calculating the pH of Strong Base Solutions
Assume 100 % Dissociation
pH dominated by OH- from the dissociation.
Let’s do #77, together!!!
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

12. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
A base does not have to contain hydroxide ion.
Many are proton acceptors &
They increase the hydroxide ion concentration
because of their reaction with water.
NH3 (aq) + H2O (l)  NH4+ (aq) + OH- (aq)
base acid
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

13. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
These bases typically have
at least one unshared pair of electrons
that is capable of forming a bond with a
proton.
Examples given on page 646.
Bases have a lone pair of electrons located
on a nitrogen atom.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

14. Substituted Ammonia Molecules
Amines
General Formula
RxN(H)3-x
Read Chemical Impact on page 648.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

15. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Bases (continued)
weak = very little dissociation (or reaction with water)
H3CNH2(aq) + H2O(l)  H3CNH3+(aq) + OH(aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

16. Base Dissociation Constant (Kb)
B (aq) + H2O(l)  BH+ (aq) + OH-(aq)
Kb = [BH+]_[OH-]
[B]
These types of Bases are Weak Bases.
Kb tend to be small.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

17. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Table of Kb found in Table 14.3
on page 647 and in Appendix.
Calculate the pH of solutions of Weak Bases
Let’s do # 83, 85a, 89b & 91 together!!!
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

18. Section 14.7 Polyprotic Acids
. . . can furnish more than one proton (H+) to the solution.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

19. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
All polyprotic acids dissociate in a stepwise
Manner -= i.e., one proton at a time.
Each step has its own equilibrium constant.
For a typical weak polyprotic acid
Ka1 > Ka2 > Ka3
i.e., each step of dissociation is
successively weaker.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

20. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
As protons are lost from polyprotic acids,
a negative charge on the acid increases.
It becomes more difficult to remove
a positively charged proton from a
negatively charged species.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

21. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Let’s look at Examples on page 650
H2CO · H3PO4
See Table 14.4 on page 651 for
Stepwise Dissociation Constants
for Common Polyprotic Acids.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

22. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
For a typical Polyprotic acid in water,
ONLY the 1st dissociation step is
Important in determining the pH.
Therefore, the pH calculation of a weak
polyprotic acid is identical to a weak
monoprotic acid.
Let’s do Problem # 95.
Homework: Extra Problem -Do #96
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

23. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
WHAT ABOUT SULFURIC ACID?
Sulfuric acid is unique:
(1) It is a strong acid in its 1st dissociation step.
H2SO4  H+ (aq) + HSO4- (aq) Ka1 = 
It is a weak acid in its second step.
HSO4- (aq)  H+ (aq) + SO42- (aq)
Ka2 = 1.2 x 10-2
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

24. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
WHAT ABOUT SULFURIC ACID?
For conc. of 1.0 M or higher,
only the 1st step makes an important
contribution.
For dilute concs. (< 1.0 M) ,the 2nd
dissociation step makes a contribution.
Let’s Do # Read Exer & p653
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

25. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Section 14.8
Acid-Base Properties of Salts
Salts = Ionic compounds
Salts can behave as ACIDS or BASES.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

26. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Salts that produce neutral solutions.
Composed of cations from strong bases
and anions from strong acids.
Example: NaCl. NaNO3, KCl
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

27. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Salts that produce basic solutions.
Composed of cations with neutral properties
and anions which are the conjugate
base of a weak acid.
Example: NaCH3COO
Major species:
Na+ is neutral
CH3COO- is conjugate base of weak acid
H2O is weakly amphoteric
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

28. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
CH3COO H2O  CH3COOH + OH1-
CH3COO1- in water produces OH1- ions
 Basic solution
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

29. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
CH3COO H2O  CH3COOH + OH1-
KB = [CH3COOH] [OH1-]
[CH3COO1-]
CH3COOH + H2O  CH3COO H1+
KA = [CH3COO1-] [ H1+]
[CH3COOH]
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

30. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
KA x KB
= [CH3COO1-] [ H1+] x [CH3COOH] [OH1-]
[CH3COOH] [CH3COO1-]
= [H1+] [OH1-]
= Kw
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

31. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
For any weak acid and its conjugate base:
Ka x Kb = Kw
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

32. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Salts that produce acidic solutions.
Composed of cations which are the
conjugate acid of a weak base and
anions with neutral properties.
Example: NH4Cl
Major species: Cl-, H2O, & NH4+
NH41+ (aq)  NH3 (aq) + H1+ (aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

33. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Let’s Do Problems # 99, 101, 103, 105a, 107
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

34. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Another type of salt gives acidic solutions
those with
Hydrated ions of highly charged metal
Dissolve AlCl3 in water.
Al(H2O)63+ is formed.
It is a weak acid.
Al(H2O)63+ (aq)  Al(OH)(H2O)52+ (aq) + H+ (aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

35. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Figure The Al(H2O)63+ Ion
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

36. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
A high charge on the metal ion (Al3+)
polarizes the O—H bonds & makes
these water molecules more acidic
than the O—H bonds ordinarily are
in water.
Let’s Do Problem # 109
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

37. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Salts with 2 ions that can affect the pH
Too complicated to deal with quantitatively.
One can predict if Acidic, Basic or Neutral
Compare Ka & Kb
If Ka > Kb, then Acidic
If Ka < Kb, then Basic
If Ka = Kb, then Neutral
Let’s Do Problem 111
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

38. Acid-Base Properties of Salts See Table 14.6 on page 660
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

39. Section 14.9 Structure and Acid-Base Properties
Read pages
Two factors for acidity in binary compounds:
Bond Polarity (high is good)
Bond Strength (low is good)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

40. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Oxyacids
H—O—X
Acid Strength Increases with an increase
in the number of oxygen atoms.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

41. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Figure The Effect of the Number of Attached Oxygens on the O-H Bond in a Series of of Chlorine Oxyacids
Electronegative oxygen
atoms pull electrons away
from the Cl atoms & the
O—H bond.
HClO4
Strongest
Acid
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

42. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Hydrated metal ions
Example: Al(H2O)63+
Greater the charge on a metal ion the
greater the acidity of the attached water molecules.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

43. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Section Acid Base Properties of Oxides
A compound containing the H—O—X group
Will produce
1. an acidic sol’n in water if the O—X bond
is strong and covalent.
Example:
H2SO4; O—S bonds are strong &
covalent. Therefore, O—H bonds break
to produce protons.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

44. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
2. a basic sol’n in water if the O—X bond
is ionic.
Example:
Na—O—H
O—Na bonds are ionic and therefore
Break in water to give Na+ & OH-
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

45. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Oxides
Acidic Oxides (Acid Anhydrides):
OX bond is strong and covalent.
Dissolve in water & form acidic sol’ns.
Non-metal oxides form acid sol’ns in water.
SO2, NO2, CrO3
EXAMPLES:
SO3 + H2O (l)  H2SO4 (aq)
SO2 + H2O (l)  H2SO3 (aq)
CO2 + H2O (l)  H2CO3 (aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

46. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Oxides
Basic Oxides (Basic Anhydrides):
OX bond is ionic.
Dissolve in water & form basic sol’ns.
Metal oxides form basic sol’ns in water.
K2O, CaO
EXAMPLES
CaO (s) + H2O (l)  Ca(OH)2 (aq)
K2O (s) + H2O (l)  2 KOH (aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

47. Section 14.11 Lewis Acids and Bases
Lewis Acid: electron pair acceptor
Lewis Base: electron pair donor
Acid
Base
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

48. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Figure The Al(H2O)63+ Ion
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

49. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Lewis Acid-Base Model –
Most general model for acid-base
behavior.
Lewis Model encompasses the Bronsted-
Lowry model, but the reverse is not
true.
Lewis Acids can be a species without H+.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.

50. Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Let’s Do Problems # 119, 121, 123, 124.
Section 14.12
Strategy for Solving Acid-Base
Problems: A Summary
READ!!!!!!!!!!!!!!!!!!!
ALSO!! Good “Review” p
Copyright©2000 by Houghton Mifflin Company. All rights reserved.