1. Ch15. Acids and Bases: A Second Look
Brady & Senese, 5th Ed 1

2. Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
4.3

3. A Brønsted acid is a proton donor A Brønsted base is a proton acceptor
conjugate acid
conjugate base
base
acid
15.1

4. (a) Formic acid transfers a proton to a water molecule
(a) Formic acid transfers a proton to a water molecule. HCHO2 is the acid and H2O is the base. (b) When a hydronium ion transfers a proton to the CHO2- ion, H3O+ is the acid and formate ion is the base.

6. 15.1. Brønsted-Lowry acids and bases exchange protons
Identify the Conjugate Partner for Each
conjugate base
conjugate acid
HCl
NH3
HC2H3O2
CN- HF
15.1. Brønsted-Lowry acids and bases exchange protons 6

7. Identify the conjugate pair for each acid/base:
Iodic acid
Nitrous acid
Acetic acid
Bisulfite ion
Hydrogen sulfate

8. 15.1. Brønsted-Lowry acids and bases exchange protons
Your Turn!
How many of the following pairs are conjugate pairs:
HCN/CN- ii. HCl/Cl- iii. H2S/S2- 1 2 3
None of them are conjugate
15.1. Brønsted-Lowry acids and bases exchange protons 8

10. d

11. d

12. An amphoteric substances can act as either an acid or base, also called amphiprotic, and can be either molecules or ions

13. 15.1. Brønsted-Lowry acids and bases exchange protons
Your Turn!
How many of the following are amphoteric?
HC2H3O2 , H2PO42-, HSO4- 1 2 3
None of these
15.1. Brønsted-Lowry acids and bases exchange protons 13

15. Strong Acid
Weak Acid
15.4

16. ACID-BASE THEORIES HOAc + H2O H3O+ + OAc-
Acetic acid is only 0.42% ionized when [HOAc] = 1.0 M. It is a WEAK ACID
HOAc H2O H3O OAc-
WEAK A base acid STRONG B
Because [H3O+] is small, this must mean
1. H3O+ is a stronger acid than HOAc
2. OAc- is a stronger base than H2O

17. Identify The Preferred Direction Of The Following
H3O+ (aq) + CO32-(aq) ↔ HCO-3(aq) + H2O (l)
NH4+(aq) + HCO-3(aq) ↔ NH3(aq) + H2CO3(aq)
Cl- + HCN(aq) ↔ HCl(aq) + CN-(aq)
H2O
HCN
H3O+
NH4+
H2CO3
Increasing Acid Strength
15.1. Brønsted-Lowry acids and bases exchange protons 17 17

18. 15.4

19. 15.1. Brønsted-Lowry acids and bases exchange protons
Your Turn!
Which reaction is not written as in the preferred direction.
HC2H3O2 + H2AsO4- ↔H3AsO4 + C2H3O2-
H3AsO4 +H2AsO3- ↔ H2AsO4- + H3AsO3
HC2H3O2 + H2AsO3- ↔C2H3O2- + H3AsO3
All are preferred as written
H2O
H3AsO3
HC2H3O2
H3AsO4
H3O+
Increasing Acid Strength
15.1. Brønsted-Lowry acids and bases exchange protons 19

20. Periodic Trends Of Binary Acids (HnX )
As we read left to right in a period, increasing electronegativity of X makes the H-X bond more polar
Acid strength increases with increasing polarity
As we read top to bottom in a group, the acid strength increases due to increasing bond length of the HX bond due to increased radius of the anion, X
ChemFAQs: How can I compare acid and base strengths?
How can I use the periodic table to compare the strengths of binary acids?
15.2. Strengths of Brønsted acids and bases follow periodic trends 20 20

21. Molecular Structure and Acid Strength
H+ + X-
H X
The stronger the bond
The weaker the acid
HF << HCl < HBr < HI
15.9

22. 15.2. Strengths of Brønsted acids and bases follow periodic trends
Learning Check
Which is a stronger acid?
H2S or H2O
CH4 or NH3
HF or HI δ- δ- δ+ δ+ δ- δ+ δ+ δ+ δ+ δ- δ-
15.2. Strengths of Brønsted acids and bases follow periodic trends 22 22

23. Oxoacids ( A(O)m(OH)n)
Increase in strength as the electronegativity of the central atom, A, increases
Increase in strength as the number of oxygen atoms on (hence the oxidation state of) the central atom, A, increases
Electrical induction through the central atom weakens strength of the bond to H
                                                                                                                          δ+ δ- δ+ δ-
ChemFAQ: How can I compare the strengths of two oxoacids, using their formulas?
15.2. Strengths of Brønsted acids and bases follow periodic trends 23 23

24. 15.2. Strengths of Brønsted acids and bases follow periodic trends
Learning Check
Which is a stronger acid?
H2SO4 or H3PO4
HNO3 or H3PO4
H2SO4 or H2SO3
HNO3 or HNO2
15.2. Strengths of Brønsted acids and bases follow periodic trends 24

25. Anions Of Oxoacids Are Basic
Oxygen atoms are electron withdrawing, thus the charge on an anion is located on the lone oxygens
The more oxygen atoms there are that share the same charge, the less basic is the anion
The stronger the base behavior of the anion, the greater the strength of the conjugate acid - -
2 O share the (-) charge
3 O share the (-) charge
15.2. Strengths of Brønsted acids and bases follow periodic trends 25

26. 15.2. Strengths of Brønsted acids and bases follow periodic trends
Your Turn!
Which statement about acid strength is false:
Binary acids get stronger as the anion gets larger
Ternary oxoacids get stronger as the central atom increases in size
Ternary acid strength increases with increasing oxidation state
None of these are false
15.2. Strengths of Brønsted acids and bases follow periodic trends 26

27. Rank by Acid Strength HI HBr HCl HF HClO4 HClO3 HClO2 HClO
HClO HBrO HIO

28. Lewis Acid/Base Reactions
Lewis acids accept an electron pair to form coordinate covalent bonds
Lewis bases donate lone pairs of electron to form coordinate covalent bonds
Neutralization is the formation of a coordinate covalent bond between the donor and acceptor
ChemFAQs: How can I tell whether a substance is likely to act as a Lewis acid?
How can I tell whether a substance is likely to act as a Lewis base?
15.3. Lewis acids and bases involve coordinate covalent bonds 28 28

29. No protons donated or accepted!
Lewis Acids and Bases F H F H
F B + •
N H
F B
N H • F H F H
acid
base
No protons donated or accepted!
15.12

31. When cations dissolve in water, they form species called hydrated ions
In general, most metal oxides react with water to form bases, and nonmetal oxides react with water to form acids
In Section 5.5 metal oxides were called base anhydrides and nonmetal oxides were called acid anhydrides
When cations dissolve in water, they form species called hydrated ions
Hydrated metal ions tend to be Brønsted acids

32. For the monohydrate of the metal ion Mn+ the equilibrium can be represented as
The metal ion makes the hydrogen on the water more acidic.

34. The charge density of a cation is its charge divided by its volume
The higher the charge density, the better a cation is at drawing electron density from a O-H bond and the more acidic it is
Within a given period, the cation size increases, and the charge density decreases, from top to bottom
As a result, the most acidic hydrated cations are found at the top of a group
As the cation charge increases, it becomes more acidic

36. Water undergoes self-ionization or autoionization making it a weak electrolyte
This equilibrium is described by the ion product of water

37. The Ion Product of Water
[H+][OH-]
H2O (l) H+ (aq) + OH- (aq)
Kc =
[H2O] = constant
[H2O]
Kc[H2O] = Kw = [H+][OH-]
The ion-product constant (Kw) is the product of the molar concentrations of H+ and OH- ions at a particular temperature.
Solution Is
[H+] = [OH-]
neutral
At 250C
Kw = [H+][OH-] = 1.0 x 10-14
[H+] > [OH-]
acidic
[H+] < [OH-]
basic
15.2

38. 15.5. pH is a measure of the acidity of a solution
Learning Check
Complete the following with the missing data
[OH-]
[H3O+] pH
3.2 × 10-3 M
2.3 × 10-5 M
1.5 × 10-2 M
2.55 × 10-6 M
ChemFAQs:
How are hydroxide and hydrogen ion concentrations related in aqueous solutions?
What is pH?
How do I estimate pH from hydrogen ion molarities?
How do I estimate pOH from hydrogen ion molarities?
How do I estimate pH from hydroxide ion molarities?
How do I estimate hydrogen ion molarity from pH?
8.50
15.5. pH is a measure of the acidity of a solution 38 38

39. 15.5. pH is a measure of the acidity of a solution
Learning Check
Complete the following with the missing data pH
pOH
[H3O+]
2.33
1.89
Thus, at room temp (25° C, 14=pH+pOH)
ChemFAQs:
How are hydroxide and hydrogen ion concentrations related in aqueous solutions?
What is pH?
How do I estimate pH from hydrogen ion molarities?
How do I estimate pOH from hydrogen ion molarities?
How do I estimate pH from hydroxide ion molarities?
How do I estimate hydrogen ion molarity from pH?
15.5. pH is a measure of the acidity of a solution 39 39

40. What is the [H3O+] in a HCl solution that has a concentration of 5
What is the [H3O+] in a HCl solution that has a concentration of 5.9E-2M? a) 5.9E-2 M b) 3.0 E-2 M c) 1.0 E-2 M d) 1.2 E-1 M e) 1.23 M
At 250C
Kw = [H+][OH-] = 1.0 x 10-14

41. 15.5. pH is a measure of the acidity of a solution
What is the pH of a solution that has a [OH-] = 1.2×10-3 M?
2.92
11.1
1.20
None of the above
15.5. pH is a measure of the acidity of a solution 41

42. At 250C
Kw = [H+][OH-] = 1.0 x 10-14
What is [OH-] in a Ba(OH)2 solution that has a concentration of 3.3E-2M? a) 1.7 E-2 M b) 3.3 E-2 M c) 6.6 E-2 M d) 1.2 E-1 M e) M

45. Indicators Help Us Estimate pH
15.5. pH is a measure of the acidity of a solution 45

46. pFUNCTIONS
pX = - log X
pH = - log [H+]
pOH = - log [OH-]
pK = -log K

47. The pH of rainwater collected in a certain region of the northeastern United States on a particular day was What is the H+ ion concentration of the rainwater?
pH = -log [H+]
15.3

48. The OH- ion concentration of a blood sample is 2. 5 x 10-7 M
The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood?
15.3

49. Strong Acids Ionize 100% in Water
As the substances are placed into water, they form H3O+ .
The H3O+ formed by the acid suppresses water’s ionization. (if [acid] > 10-7 M)
The pH can be calculated from the concentration of H3O+ produced by the strong acid
The reaction of strong acids occurs irreversibly, so we show the reaction with a → instead of using a double arrow
ChemFAQ: How do I estimate pH for a strong acid solution?
15.6. Strong acids and bases are fully dissociated in solution 49 49

50. 15.6. Strong acids and bases are fully dissociated in solution
Learning Check
What is the pH of 0.1M HCl
15.6. Strong acids and bases are fully dissociated in solution 50 50

51. 15.6. Strong acids and bases are fully dissociated in solution
Learning Check
What is the pH of 0.1M HCl
HCl(aq) + H2O(l) →H3O+(aq) + Cl-(aq)
0.1 N/A 0 0 I C
0 N/A end
pH = -log(0.1) = 1
15.6. Strong acids and bases are fully dissociated in solution 51 51

52. Strong Bases Dissociate 100% In Water
They are strong electrolytes that form OH- when dissolved
pOH can be calculated from the [OH-] from the solution
Water’s contribution is negligible if the base is sufficiently concentrated [OH-]>10-7M
ChemFAQ: How do I estimate pH for a strong base solution?
15.6. Strong acids and bases are fully dissociated in solution 52 52

53. 15.6. Strong acids and bases are fully dissociated in solution
What is the pH of 0.5M Ca(OH)2?
15.6. Strong acids and bases are fully dissociated in solution 53 53

54. 15.6. Strong acids and bases are fully dissociated in solution
What is the pH of 0.5M Ca(OH)2?
Ca(OH)2(aq) → Ca2+(aq) + 2OH-(aq) I
×2 C E
pOH = -log(1.0) =0
pH = 14
15.6. Strong acids and bases are fully dissociated in solution 54 54

55. 15.6. Strong acids and bases are fully dissociated in solution
Your Turn!
What is the pH of a 0.50M solution of NaOH?
0.500
0.301
13.7
None of these
15.6. Strong acids and bases are fully dissociated in solution 55

56. What is the pH of an NaOH solution that has a concentration of 3
What is the pH of an NaOH solution that has a concentration of 3.3E-3 M? a) b) 2.48 c) d) 1.2 E+1, e) 12.52,

57. What is the final pH, if 200 mL of 3
What is the final pH, if 200 mL of 3.3E-2 M HNO3 is diluted with water to a final volume of 328 mL? a) b) 2.0E-2 c) 5.4E-2 d) e) 1.69

58. What is the pH of a 3. 3E-2 M Ba(OH)2 solution. a) -1. 48 b) -1
What is the pH of a 3.3E-2 M Ba(OH)2 solution? a) b) c) d) e)

59. In a pure aqueous solution of NaOH, the pH was measured to be 13. 41
In a pure aqueous solution of NaOH, the pH was measured to be What is the molar concentration of NaOH? a) 3.9E-14 M b) 5.7E-1 M c) 0.26 M d) 0.48 M e) 2.6E13 M

60. What is the final molarity of [H3O+], if 100 mL of 7
What is the final molarity of [H3O+], if 100 mL of 7.0E-2 M HCl is diluted with 236 mL of distilled water? a) 3.0E-4 M b) 2.1E-2 M c) 3.0E-2 M d) 1.7E-1 M e) 2.4E-1 M

61. Exactly 100 mL of 0. 20 M NaOH was mixed with 125 mL of 0. 20 M HCl
Exactly 100 mL of 0.20 M NaOH was mixed with 125 mL of 0.20 M HCl. What is the molarity of the NaCl formed? a) 1.6E-1 M b) 1.8E-1 M c) 1.8E-2 M d) 8.9E-2 M e) 0.20 M

62. Exactly 100 mL of 0. 20 M NaOH was mixed with 125 mL of 0. 20 M HCl
Exactly 100 mL of 0.20 M NaOH was mixed with 125 mL of 0.20 M HCl. What is the pH of this mixture ? a) 0.70 b) 0.80 c) 1.65 d) 1.80 e) 7.80

63. Exactly 100 mL of 0. 20 M NaOH was mixed with 118 mL of 0. 30 M HCl
Exactly 100 mL of 0.20 M NaOH was mixed with 118 mL of 0.30 M HCl. What is the pH of this mixture? a) 0.80 b) 1.15 c) d) 3.12 e) 12.45

64. b

65. a

66. a

67. a

68. d