1. 14.1 Intro to Acids and Bases 14.2 Acid Strength 14.3 pH Scale
Ch. 14: Acids and Bases
14.1 Intro to Acids and Bases
14.2 Acid Strength
14.3 pH Scale

2. Definitions Arrhenius Bronsted-Lowry
______: produce H+ in aqueous solution
______: produces OH- in aqueous solution
very limited
Bronsted-Lowry
______: H+ donor
______: H+ acceptor
more general

3. Conjugate Acid-Base Pair
HA(aq) + H2O(l) ⇄ H3O+(aq) + A-(aq)
2 substances that are connected by a donating and accepting of H2O
really a “fight” over H+ between two bases: ______ and ______
if A- has a greater attraction, rxn lies to _____
if H2O has greater attraction, rxn lies to _____
This helps with #29 on HW

4. Acid dissociation constant (Ka)
equilibrium expression where H+ is removed to form conjugate base
HA + H2O ⇄ H3O+ + A-
Don’t include H2O

5. Strength determined by equilibrium position of dissociation reaction
strong acid:
lies far to right, almost all HA is _____________.
________________
creates weak conjugate base
weak acid:
lies far to left, almost all HA is stays as _____.
creates strong conjugate base
This helps with #33 on HW

7. Water is a stronger base than the CB of a strong acid but a weaker base than the CB of a weak acid
Water is a stronger acid than the CA or a strong base but a weaker acid than the CA if a weak base

8. Types of Acids __________: an acid with 2 acidic protons
__________: ex. HNO3
most acids are this type
where the acidic proton is attached to an oxygen
_________________: ex. CH3COOH
containing a carboxyl group
usually weak
_________________: ex. HBr
hydrogen and a halogen

9. Autoionization 2 water molecules exchange H+ H2O + H2O ⇄ H3O+ +OH- Kw=
dissociation constant for water
at 25C, [H+]=[OH-]=1.0 x 10-7
so at 25C, Kw=1.0x10-14
How will change it with temperature?

10. pH scale pH= pOH= [H+]= [OH-]= pH ____________ as [H+] ______________
This helps with #37, 41, 43 on HW

11. Example 1
Write the ionization or dissociation reaction and the Ka expression for each of the following:
acetic acid – (HCH3COO)
ammonium ion – (NH4+)

12. Example 2
Determine the acid, base, conj. acid, and conj. base in each reaction:
NH4+(aq) + CN-(aq) ⇄ HCN(aq) + NH3(aq
(CH3)3N(aq) + H2O(l) ⇄ (CH3)3NH+(aq) + OH-(aq)
HCHO2(aq) + PO43-(aq) ⇄ CHO2-(aq) + HPO42-(aq)

13. Example 3 Determine which species is a stronger base: F- or Cl-
Determine which species is a stronger acid: H2O or NH4+

14. Example 4
The [OH-] of a solution at 25C is 1.0 x 10-5 M. Determine the [H+], pH and pOH.

15. Example 5
The pH of a solution at 25C is Calculate the pOH, [OH-] and [H+].

16. 14.4-5 pH of Acidic Solutions
Ch. 14: Acids and Bases
pH of Acidic Solutions

17. Strong Acids
SA completely form ions so you do not need to use Ka and I-C-E chart
Finding the pH of 0.10 M HNO3
Always write the important species present at the beginning of each problem
H+ , NO3-, H2O
water will exist as H+ and OH- but only a small amount- so it can be ignored
HNO3  H+ + NO3-
[H+] = 0.10 M
pH = -log(0.10) = 1.00

18. Strong Acids
Find the pH of 1.0 x M HCl

19. Weak Acids Write major species Decide on which can provide H+ ions
Make ice chart
Put equilibrium values in Ka expression
Check validity of assumption (x must be less than 5% of initial conc)
Find pH

20. Weak Acids- Example
Calculate the pH of 1.00 M solution of HF (Ka = 7.2 x 10-4)

21. Weak Acids- Example
HF  H F- I C E

22. Weak Acids- Example
Check assumption:
pH =

23. Weak Acid- Example 2 HOCl  H+ + OCl-
Find pH of M solution of HOCl (Ka = 3.5x10-8)
HOCl, H2O
HOCl will provide much more H+ than H2O – ignore H2O
HOCl  H OCl- I C E

24. Weak Acid- Example 2
Check assumption:
pH =

25. Mixtures of Weak Acids
When dealing with a mixture of acids, consider the strongest acid first
then, use the “Equilibrium” values from it to begin your weaker acid

26. Mixtures of Weak Acids
Find the pH of a mixture of 1.00 M HCN (Ka=6.2x10-10) and 5.00 M HNO2 (Ka=4.0x10-4)
HNO2 is most important b/c it has highest Ka value
HNO2  H NO2- I C E

27. Mixtures of Weak Acids
HCN  H CN- I C E

28. Mixtures of Weak Acids [H+]= pH = [CN-] =
Find the [CN-] at equilibrium
[CN-] =

29. Percent Dissociation also called Percent Ionization
for a weak acid, the % dissociation increases as molarity decreases
dilution shifts equilibrium to side with greater number of particles

30. Percent Dissociation

31. Calculate Percent Dissociation
for 1.0 M acetic acid (Ka=1.8x10-5)
CH3COOH  H CH3COO- I C E

32. Calculate Percent Dissociation

33. Calculate Percent Dissociation
For M CH3COOH

34. Percent Dissociation
In a M solution of a weak acid, 2.5% of the acid is dissociated. Find the Ka.

35. HA  H A- I C E

36. Ch. 14: Acids and Bases
14.6 Bases

37. Bases

38. Bases Strong Bases Find pH of 5.0x10-2 M NaOH solution
What would be another way to get pH?
What if it was a Ca(OH)2 solution?

39. Bases Weak Bases do not contain OH- accepts H+ from H2O to make OH-
usually have at least one unshared pair of electrons
used to form bond with hydrogen

40. B(aq) + OH-(l)  BH+(aq) + OH-(aq)
Bases Kb
refers to reaction of base with water to make conjugate acid and OH-
for weak bases only
B(aq) + OH-(l)  BH+(aq) + OH-(aq)

41. Example Find the pH for 15.0 M solution of NH3 (Kb = 1.8x10-5)
NH3 will create more OH- than water so autoionization can be ignored
NH H2O  NH OH- I C E

42. Example

43. Example
Codeine (C18H21NO3) is a weak organic base. A 5.0x10-3 M solution of codeine has a pH of Calculate the Kb for this substance.
What is the chemical reaction?

44. Example
C18H21NO3 + H2O ⇄ HC18H21NO3+ + OH- I C E
x = [OH-] = 8.9x10-5

45. Ch. 14: Acids and Bases
14.7 Polyprotic Acids

46. Polyprotic Acids acids that can donate more than one H+
always dissociate one at a time
Example: carbonic acid
Ka1= 4.3x10-7
Ka2 = 5.6x10-11
Ka1 > Ka2 > Ka3 for
typical weak polyprotic
acid

47. Important Polyprotic Acids
phosphoric acid: H3PO4
only 1st step creates important amount of H+
sulfuric acid: H2SO4
1st step is strong (H2SO4 is a strong acid)
2nd step is weak (HSO4- is a weak acid)

48. Example Find the pH of a 1.00x10-2 M sulfuric acid solution
H+, HSO4-, H2O
From 1st dissociation, [H+]= 1.00x10-2 M
HSO4-  SO H+ I C E

49. Example

50. 14.8 Acidic and Basic Properties of Salts
Ch. 14 Acids and Bases
14.8 Acidic and Basic Properties of Salts

51. Salts another word for ionic compounds
when soluble salts are dissolved, they break up into ions that can be either acidic or basic
the acidic or basic ions make the solution acidic or basic

52. Determining A/B of a Salt
Figure out what each ion in the salt comes from
Ex: KCN
K+ comes from strong base, _______
CN- comes from weak acid, _______
Determine what quality that gives each ion
K+ must be weak _________
CN- must be strong _________
Compare and determine the overall acidity or basicity of solution
overall: ____________________

53. Cations Weak Conj. Acid Strong Conj. Acid from Strong B K+, Ca2+
from KOH and Ca(OH)2
Strong Conj. Acid
from weak B
NH4+, C5H5NH+
from NH3 and C5H5N
and highly charged metal ions (Al3+ or Fe3+)

54. Anions weak Conj. Base strong Conj. Base from Strong Acid Cl-, HSO4-
from HCl and H2SO4
strong Conj. Base
from Weak Acid
HCO32-, NO2-
from H2CO3 and HNO2

55. Acidic and Basic?
If it is difficult to tell the overall quality, compare the K values to determine the type of solution
Ka > Kb : _________
Kb > Ka : _________
Ka*Kb = Kw
for any weak acid and
its CB

56. Practice
Predict which of the following will be acidic, basic or neutral
NH4Br
NH4+
Br-
overall:
FeCl3
Fe+3
Cl-

57. Practice
Na2CO3
Na+
CO32-
overall:
KClO4 K+
ClO4
NaHC2O4
HC2O4-

58. Example Find the pH of a 0.20 M solution of KF. KF  K+ + F-
which of these will effect the pH of the solution?
F- + H2O  HF OH- I C E

59. Example

60. Summary

61. Ch. 14 Acids and Bases
14.9 Structure

62. Why are some H’s acidic? acidic: non-acidic weak bonds strong bonds
polar bonds
non-acidic
strong bonds
nonpolar bonds

63. Factors in Acidity
Overall: the ______________ the bond to the H is, the ___________ the acid is
If the atoms around the bond are more electronegative, they will pull electron density away from the bond
that will make the bond weaker
Electronegativity of halogen
the more electronegative the halogen is, the more polar the bond is, and the stronger the acid is

64. Factors in Acidity Size of atoms
the ___________ the atoms, the weaker the bond, the ___________the acid
Ex: H-F, H-Cl, H-Br, H-I
H-F has the most polar bond but it is a weak acid- Why?
H and F are both tiny atoms so have a stronger attraction to each other
H-I has very weak bond b/c I is large so is a strong acid

65. Factors in Acidity Number of Oxygens in Oxyacid
the _________ the number of oxygens, the more polar the bond is, the _________ the acid is

66. Example Which is the stronger acid? Explain HNO2 or HClO2 HNO3 or HNO2
CCl3COOH or CH3COOH

67. Ch. 14 Acids and Bases
14.10 Oxides

68. H-O-X If X is relatively electronegative If X is not electronegative
H-O bond is weaker and breaks easily
HOX 
If X is not electronegative
O-X bond will break

69. Acidic Oxides
when a covalent oxide dissolves in water, an acidic solution forms
Ex: SO2, CO2, NO2
how do you determine what acid is formed?
be sure the nonmetal atom keeps the same oxidation state
SO2 + H2O 

70. Basic Oxides
when an ionic oxide dissolves in water, a basic solution forms
Na2O, CaO, K2O
Na2O + H2O 

71. Ch. 14 Acids and Bases
14.11 Lewis Acid-Base Model

72. Lewis Model even more general than Bronsted-Lowry acid base
electron pair ____________
has empty atomic orbitals
base
has lone pair

74. Examples
Al3+ + 6H2O  [Al(H2O)6]3+
SO3 + H2O  H2SO4