1. Chapter 9: Acids & Bases

2. Acids
Acid: a substance that, when dissolved in water, increases the H+ (or H3O+) concentration of the solution by giving up (or donating) a H+
HCl(aq) + H2O(l) H3O+(aq)+ Cl-(aq)
HCl (aq) H+ (aq) + Cl- (aq)
Can be strong or weak
Monoprotic or polyprotic (protic ~ proton~H+)
Arrow pushing mechanism

5. Chapter 15, Unnumbered Figure, Page 660

6. Hydrogens connected to more electronegative atoms are more likely to act as an acidic hydrogen
High EN atoms: F, Cl, Br, I, O
Chapter 15, Unnumbered Figure 1, Page 661

8. Practice
Decide if the following molecules are acids or not, based on their structures.

9. Strong acid: an acid that completely ionizes/dissociates in water
HNO3(aq) + H2O(l) H3O+(aq) + NO3-(aq)

10. Weak Acid: an acid that only partially ionizes/dissociates in water
HC2H3O2(aq)+ H2O(l) C2H3O2-(aq) +H3O+(aq)
Weak Acids:
Phosphoric acid H3PO4
Acetic Acid CH3COOH
Carbonic Acid H2CO3
Hydrocyanic Acid HCN
Benzoic Acid C6H5COOH

12. Chapter 15, Unnumbered Figure 2, Page 661

13. Chapter 15, Unnumbered Figure 4, Page 661

14. Practice
Write the chemical equation for the dissociation of each acid in the following containers.
Then determine whether there is strong or weak acid present.
Chapter 15, Unnumbered Figure 1, Page 709

15. Bases
Base: a substance that, when put in water, increases the concentration of OH- ions or a substance that accepts H+ ions
NaOH(aq) + H2O(l) Na+(aq) + OH-(aq) +H2O
NaOH(aq) Na+(aq) + OH-(aq)
Strong Bases: bases that completely ionize in water
Arrow pushing mechanism

18. Weak Bases: bases that only partially ionize in water
Ammonia: NH3
Pyridine: C5H5N

22. Chapter 15, Unnumbered Figure, Page 662

23. Chapter 15, Unnumbered Figure, Page 686

24. Then determine whether there a strong or weak base present.
Write the chemical equation for the dissociation of each base in the following containers.
Then determine whether there a strong or weak base present.
Chapter 15, Unnumbered Figure 2, Page 709

25. Polyprotic Acids
Polyprotic acids: acids that can release more than one H+
HCl(aq) +H2O(l) Cl-(aq) + H3O+(aq)
HCl = monoprotic acid
Complete ionization of H2SO4 (sulfuric acid)
H2SO4(aq) + H2O(l) HSO4-(aq) + H3O+(aq)
HSO4-(aq) + H2O(l) SO42-(aq) + H3O+(aq)
H2SO4 = polyprotic acid

27. Problem
Write out the equation(s) for the complete ionization of phosphoric acid, H3PO4, in water.

28. Each acid has a conjugate base and every base has a conjugate acid
Congugate Acid-Base Pairs
Each acid has a conjugate base and every base has a conjugate acid
conjugate acid-base pair 1
HA + B A− + BH+
conjugate acid-base pair 2

30. Problems Identify the conjugate bases for the following: HBr H2S H2CO3
Identify the conjugate acids for the following
NO2-
NH3
OH-

31. In the following equations, identify the conjugate acid and base pairs:
HCl + H2O  H3O+ + Cl-
C5H5N + H2O  C5H6N+ + OH-

33. Acid Ionization Constant
Acid Ionization Constant (Ka): the equilibrium constant for the ionization reaction of an acid with water
HA + H2O A- + H3O+
Large Ka = Strong acid
Small Ka = Weak acid

37. Questions
Write the equilibrium constant expression for the dissociation of HCN (hydrocyanic acid) in water
Write the equilibrium expression for the dissociation of HF in water
If the Ka for HCN is 4.9 x and the Ka for HF is 7.2 x 10-4, which acid is stronger?

38. Predict whether the equilibrium for each of the following reactions favors the reactants or products.
H3PO4(aq) + H2O(l) H3O+(aq) + H2PO4(aq)
NH4+(aq) + H2O(l) H3O+(aq) + NH3(aq)

39. Base Ionization Constant
Base Ionization Constant (Kb): the equilibrium constant for the ionization reaction of a base with water
B + H2O OH- + BH+
Large Kb = Strong base
Small Kb = Weak base

41. Autoionization of Water

42. Autoionization of Water
Also called “Self Ionization”
About 1 out of every 10 million water molecules form ions through self ionization
H2O Û H+ + OH–
H2O + H2O Û H3O+ + OH–
All aqueous solutions contain both H3O+ and OH–

43. Ion Product Constant for Water
Ion Product Constant for Water (Kw): the numerical value obtained by multiplying the molar concentrations for hydronium and hydroxide ions present in pure water at 25°C
Kw = [H3O+][OH-] = 1.00 x at 25 oC
the concentration of H3O+ and OH– are equal in pure water
[H3O+] = [OH–] = 25°C

44. Ion Product of Water
the product of the H3O+ and OH– concentrations is always the same number
Kw =[H3O+][OH–] = 1.00 x 25°C
if you measure one of the concentrations, you can calculate the other
as [H3O+] increases the [OH–] must decrease so the product stays constant
inversely proportional

45. H+ OH- [H+] vs. [OH-] Acid Base
Even though it may look like it, neither H+ nor OH- will ever be 0

46. Acidic and Basic Solutions
Neutral solutions have equal [H3O+] and [OH–]
[H3O+] = [OH–] = 1 x 10-7
acidic solutions have a larger [H3O+] than [OH–]
[H3O+] > [OH–]
[H3O+] > 1 x 10-7; [OH–] < 1 x 10-7
basic solutions have a larger [OH–] than [H3O+]
[H3O+] < [OH–]
[H3O+] < 1 x 10-7; [OH–] > 1 x 10-7

47. Questions
Calculate the [OH] at 25°C when the [H3O+] = 1.5 x 10-9 M, and determine if the solution is acidic, basic, or neutral
Calculate the [H3O+] at 25°C in a solution that has a [OH] 1.3 x M and determine if the solution is acidic, basic, or neutral
Calculate the [H3O+] at 25°C in a solution that has a [OH] 1.0 x 10-7 M and determine if the solution is acidic, basic, or neutral

48. pH and pOH Acidic solutions Basic solutions Neutral solutions

50. pH is a measure of the concentration of H+ or H3O+ in solution
pH = -log [H+] OR pH = -log [H3O+]
[H3O+] = 10-pH
pOH is a measure of the concentration of OH- in solution
pOH = -log [OH-]
[OH-] = 10-pOH
pH + pOH = 14

51. Problems
What is the pH for an HCl solution with an [H3O+] = 2.3 x 10-2?
What is the pH of an NaOH solution with an [H3O+] = 3.39 x 10-10?
What is the pH of a KOH solution with a [OH-] = 1.1 x 10-2?
What is the [H3O+] for a solution with a pH of What is the [OH-]?

52. Classification of Water Soluble Substances
Electrolytes: solutes that separate into ions when dissolved in water (they’re soluble)
Have the ability to conduct electricity
2 types
Strong electrolytes
Weak electrolytes

53. Strong electrolytes: solutes that completely dissociates into ions when dissolved in water
Examples: NaCl, MgBr2, HCl
Strong electrical conductors
Strong electrolyte(aq or s) → Cation+(aq) + Anion-(aq)
Example: NaCl(s) → Na+(aq) + Cl-(aq)

54. Weak Electrolytes: solutes that, when dissolved in water, only partially dissociates into ions
Examples: HF, NH3, acetic acid
Weak electrical conductors
Weak electrolyte(aq) ↔ Cation+(aq) + Anion-(aq)
Example: HF(aq) ↔ H+(aq) + F-(aq)

55. Nonelectrolytes: solutes that dissolve in water without separating into ions
Examples: sucrose, ethanol
Do not conduct electricity
Nonelectrolyte (s or l) → Nonelectrolyte(aq)
Example: C12H22O11(s) → C12H22O11(aq)

56. Problems
The following salts are strong electrolytes. Write a balanced equation for their dissociation in water
LiBr
FeCl3
HCN is a weak acid. Write a balanced equation for its dissociation in water
Do you expect Fructose (C6H12O6) to be a strong electrolyte, weak electrolyte, or nonelectrolyte? Write a balanced equation for its solvation in water

57. Neutralization Reactions
When strong acids and bases in aqueous solution react with each other, they form water and a salt
HX(aq) + MOH(aq)  HOH(l) + MX(aq)
HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
Water
Salt

58. Problems Write out the chemical equations for the following reactions
HBr and KOH
HCl and Mg(OH)2
H2SO3 and NaOH

59. Titration
Titration: a procedure for the quantitative analysis of a substance of unknown concentration whereby a measured quantity of another substance, of known concentration, is completely reacted with the with the original substance.
Often used to determine the concentration of acids and bases

61. Equivalence point: the point in a titration at which one reactant has been exactly consumed by the addition of another reactant
Midpoint of vertical rise
Occurs at pH = 7 in a strong acid-strong base titration
[H3O+] = [OH-]

62. Indicators
Acid-Base Indicator: a chemical that changes color with a change in pH
Added to solutions in small amounts in order to determine to solution’s pH visually
Usually organic compounds
Weak acid or base
establishes an equilibrium with the H2O and H3O+ in the solution 62

63. HInd(aq) + H2O(l)  Ind(aq) + H3O+(aq)

64. Phenolphthalein 64 64

65. Bromocresol Green
Yellow
Green
Blue

66. Methyl Red 66

68. 3 steps to solving a titration problem (unknown acid molarity)
1. How many moles of base were added to titrate the unknown acid?
Use concentration and volume of base added
M =mol/L
2. What is the molar ratio that the base reacts with the acid, this will give you moles of acid?
Use the overall/net chemical equation, just like stoichiometry
3. With the moles of acid, what is the initial concentration of the acid?
Use the initial volume of acid
M = mol/L

69. Questions
You have 25.0 mL of a HCl solution of unknown concentration. If you titrate your acid with 17.3 mL of a M NaOH solution, what is the original concentration of your acid?
NaOH +HCl  H2O + NaCl
M = mol/L  M x L = mol
MNaOH x LNaOH = molNaOH
MNaOH = MNaOH
LNaOH = LNaOH
LHCl = LHCl
molNaOH x (1 molHCl / 1 molNaOH) = molHCl
molHCl / LHCl = MHCl
0.877 MNaOH x LNaOH =
molNaOH
molNaOH x (1 molHCl / 1 molNaOH) =
molHCl
molHCl / LHCl =
0.607 MHCl

70. 2). You also have 25. 0 mL of a sulfuric acid solution
2) You also have 25.0 mL of a sulfuric acid solution. If you titrate this solution with 32.1 mL of a 1.50 M KOH solution, what is the concentration of your acid?

71. Chapter 9 review
Acid, strong acid, weak acid, Base, strong base, weak base
Polyprotic acids
Acid-conjugate base, Base-conjugate acid
Neutralization reaction
Acid ionization constant, Base ionization constant
Auto ionization of water
Strong and weak electrolytes
pH and pOH
Titration, acid-base indicators, equivalence point,

72. Definitions 8 and 9 Chapter 8 Solution, solvent, solute
Solubility, Henry’s Law
Unsaturated, saturated, and super saturated solutions
Concentration, Molarity
Osmosis, osmotic pressure, turgor,
Hypotonic, hypertonic, and isotonic solutions
Mixture, colloids, suspension
Chapter 9
Acid, strong acid, weak acid, Base, strong base, weak base
Polyprotic acids
Acid-conjugate base, Base-conjugate acid
Neutralization reaction
Acid ionization constant, Base ionization constant
Auto ionization of water
Strong and weak electrolyte
pH and pOH
Titration, acid-base indicators, equivalence point,