1. Section 18.1 Introduction to Acids and Bases
Identify the physical and chemical properties of acids and bases.
Classify solutions as acidic, basic, or neutral.
Compare the Arrhenius, Brønsted-Lowry, and Lewis models of acids and bases.
Lewis structure: a model that uses electron-dot structures to show how electrons are arranged in molecules
Section 18-1

2. Section 18.1 Introduction to Acids and Bases (cont.)
acidic solution
basic solution
Arrhenius model
Brønsted-Lowry model
conjugate acid
conjugate base
conjugate acid-base pair
amphoteric
Lewis model
Different models help describe the behavior of acids and bases.
Section 18-1

3. Properties of Acids and Bases
_______ taste sour. ______ taste bitter and feel slippery.
Acids and bases are ________________.
Acids and bases can be identified by their reactions with some ___________________
Section 18-1

4. Properties of Acids and Bases (cont.)
__________ turn blue litmus red.
__________ turn red litmus blue.
Magnesium and zinc react with acids to produce _______________
Geologists identify limestone because it produces bubbles of carbon dioxide when exposed to hydrochloric acid.
Section 18-1

5. Properties of Acids and Bases (cont.)
All water solutions contain hydrogen ions (H+) and hydroxide ions (OH–).
An ____________contains more hydrogen ions than hydroxide ions.
A ________________contains more hydroxide ions than hydrogen ions.
Section 18-1

6. Properties of Acids and Bases (cont.)
The usual solvent for acids and bases is water—water produces equal numbers of hydrogen and hydroxide ions in a process called ________________
H2O(l) + H2O(l) ↔ H3O+(aq) + OH–(aq)
The hydronium ion is H3O+.
Section 18-1

7. The Arrhenius Model
The ____________states that an acid is a substance that contains hydrogen and ionizes to produce hydrogen ions in aqueous solution, and a base is a substance that contains a hydroxide group and dissociates to produce a hydroxide ion in solution.
Section 18-1

8. The Arrhenius Model (cont.)
Arrhenius acids and bases
____________ ionizes to produce H+ ions.
HCl(g) → H+(aq) + Cl–(aq)
__________dissociates to produce OH– ions.
NaOH(s) → Na+(aq) + OH–(aq)
Some solutions produce hydroxide ions even though they do not contain a hydroxide group.
Section 18-1

9. The Brønsted-Lowry Model
The __________________of acids and bases states that an acid is a hydrogen ion donor, and a base is a hydrogen ion acceptor.
The ______________________is a more inclusive model of acids and bases.
Section 18-1

10. The Brønsted-Lowry Model (cont.)
A ______________is the species produced when a base accepts a hydrogen ion.
A ______________is the species produced when an acid donates a hydrogen ion.
A ________________consists of two substances related to each other by donating and accepting a single hydrogen ion.
Section 18-1

11. The Brønsted-Lowry Model (cont.)
Hydrogen fluoride—a Brønsted-Lowry acid
HF(aq) + H2O(l) ↔ H3O+(aq) + F–(aq)
HF = acid, H2O = base, H3O+ = conjugate acid, F– = conjugate base
Section 18-1

12. The Brønsted-Lowry Model (cont.)
Ammonia— Brønsted-Lowry base
NH3(aq) + H2O(l) ↔ NH4+(aq) + OH–(aq)
NH3 = base, H2O(l) = acid, NH4+ = conjugate acid, OH– = conjugate base
Water and other substances that can act as acids or bases are called _________________.
Section 18-1

13. Monoprotic and Polyprotic Acids
An acid that can donate only one hydrogen ion is a _______________.
Only ionizable _____________ atoms can be donated.
Section 18-1

14. Monoprotic and Polyprotic Acids (cont.)
Acids that can donate more than one hydrogen ion are ______________.
Section 18-1

15. The Lewis Model
According to the ___________, a Lewis acid is an electron-pair acceptor and a Lewis base is an electron pair donor.
The Lewis model includes all the substances classified as Brønsted-Lowry acids and bases and many more.
Section 18-1

16. Write a balanced equation for aluminum and sulfuric acid.
Example Problem:
Write a balanced equation for aluminum and sulfuric acid.
Section 18-1

17. A B C D Section 18.1 Assessment A Lewis acid is a(n) ____.
A. electron pair donor
B. hydrogen ion donor
C. electron pair acceptor
D. substance that contains an hydroxide group A B C D
Section 18-1

18. A B C D Section 18.1 Assessment A conjugate acid is formed when:
A. a base accepts a hydrogen ion
B. an acid accepts a hydrogen ion
C. an acid donates a hydrogen ion
D. a base donates a hydrogen ion A B C D
Section 18-1

19. Section 18.2 Strengths of Acids and Bases
Relate the strength of an acid or base to its degree of ionization.
electrolyte: an ionic compound whose aqueous solution conducts an electric current
Compare the strength of a weak acid with the strength of its conjugate base.
Explain the relationship between the strengths of acids and bases and the values of their ionization constants.
Section 18-2

20. Section 18.2 Strengths of Acids and Bases (cont.)
strong acid
weak acid
acid ionization constant
strong base
weak base
base ionization constant
In solution, strong acids and bases ionize completely, but weak acids and bases ionize only partially.
Section 18-2

21. Acids that ionize completely are _____________
Strengths of Acids
Acids that ionize completely are _____________
Because they produce the maximum number of hydrogen ions, strong acids are good conductors of _______________.
Section 18-2

22. Strengths of Acids (cont.)
Acids that ionize only partially in dilute aqueous solutions are called __________.
Section 18-2

23. Strengths of Acids (cont.)
With a strong acid, the conjugate base is a ____________.
Equilibrium lies almost completely to the ___________ in the equation because the conjugate base has a weaker attraction for the H+ ion than does the base in the forward reaction.
In a weak acid, the ionization equilibrium lies to the far ________in the ionization equation because the conjugate base has a greater attraction for H+ ions than does the base in the forward reaction.
Section 18-2

24. Strengths of Acids (cont.)
The equilibrium constant, Keq, provides a quantitative measure of the degree of ionization of an acid.
The _______________________is the value of the equilibrium constant expression for the ionization of a weak acid, Ka.
Ka indicates whether products or reactants are favored at equilibrium.
Section 18-2

25. Strengths of Acids (cont.)
For weak acids, the products tend to be smaller compared to the un-ionized molecules (reactant).
Weaker acids have a smaller Ka.
Section 18-2

26. A ___________ionizes only partially in dilute aqueous solution.
Strengths of Bases
A base that dissociates completely into metal ions and hydroxide ions is known as a _______________.
A ___________ionizes only partially in dilute aqueous solution.
Section 18-2

27. Strengths of Bases (cont.)
The base ionization constant, Kb, is the value of the equilibrium constant expression for the ionization of a base.
Section 18-2

28. Example Problem:
Write the ionization equation and base ionization constant expression for the following base:
Hexylamine: (C6H13NH2)
Answer:
C6H13NH2(aq)+H20(l)↔C6H13NH3-(aq)+OH-(aq)

29. A B C D Section 18.2 Assessment A solution with a small Kb is a ____.
A. weak acid
B. weak base
C. strong acid
D. strong base A B C D
Section 18-2

30. A B C D Section 18.2 Assessment
Where is the equilibrium point in the ionization equation for a strong acid?
A. far right
B. far left
C. slightly right
D. slightly left A B C D
Section 18-2

31. Section 18.3 Hydrogen Ions and pH
Explain pH and pOH.
Le Châtelier’s principle: states that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress
Relate pH and pOH to the ion product constant for water.
Calculate the pH and pOH of aqueous solutions.
ion product constant for water pH
pOH
pH and pOH are logarithmic scales that express the concentrations of hydrogen ions and hydroxide ions in aqueous solutions.
Section 18-3

32. Ion Product Constant for Water
Pure water contains equal concentrations of H+ and OH– ions.
The ion production of water, Kw = [H+][OH–].
The ____________________________is the value of the equilibrium constant expression for the self-ionization of water.
Section 18-3

33. Ion Product Constant for Water (cont.)
With pure water at 398 K, both [H+] and [OH–] are equal to 1.0 × 10–7M.
Kw at 298 K = 1.0 × 10–14
Kw and LeChâtelier’s Principle proves [H+] × [OH–] must equal 1.0 × 10–14 at 298 K, and as [H+] goes up, [OH–] must go down.
Section 18-3

34. pH and pOH
Concentrations of H+ ions are often small numbers expressed in exponential notation.
_____ is the negative logarithm of the hydrogen ion concentration of a solution. pH = –log [H+]
Section 18-3

35. The sum of pH and pOH equals 14.
pH and pOH (cont.)
pOH of a solution is the negative logarithm of the hydroxide ion concentration.
pOH = –log [OH–]
The sum of pH and pOH equals 14.
Section 18-3

36. pH and pOH (cont.)
For all strong monoprotic acids, the concentration of the acid is the concentration of H+ ions.
For all strong bases, the concentration of the OH– ions available is the concentration of OH–.
Weak acids and weak bases only partially ionize and Ka and Kb values must be used.
Section 18-3

37. pH and pOH (cont.)
Litmus paper and a pH meter with electrodes can determine the pH of a solution.
Section 18-3

38. Example Problem:
Calculate the pH of the solution with the following [H+] at 298K:
[H+]=0.0055M

39. A B C D Section 18.3 Assessment
In dilute aqueous solution, as [H+] increases:
A. pH decreases
B. pOH increases
C. [OH–] decreases
D. all of the above A B C D
Section 18-3

40. A B C D Section 18.3 Assessment
What is the pH of a neutral solution such as pure water?
A. 0
B. 7
C. 14
D. 1.0 × 10–14 A B C D
Section 18-3

41. Section 18.4 Neutralization
Write chemical equations for neutralization reactions.
stoichiometry: the study of quantitative relationships between the amounts of reactants used and products formed by a chemical reaction; is based on the law of conservation of mass
Explain how neutralization reactions are used in acid-base titrations.
Compare the properties of buffered and unbuffered solutions.
Section 18-4

42. Section 18.4 Neutralization (cont.)
neutralization reaction
salt
titration
titrant
equivalence point
acid-base indicator
end point
salt hydrolysis
buffer
buffer capacity
In a neutralization reaction, an acid reacts with a base to produce a salt and water.
Section 18-4

43. Reactions Between Acids and Bases
A ____________________is a reaction in which an acid and a base in an aqueous solution react to produce a salt and water.
A ___________ is an ionic compound made up of a cation from a base and an anion from an acid.
Neutralization is a ____________________
Section 18-4

44. Reactions Between Acids and Bases (cont.)
Section 18-4

45. Reactions Between Acids and Bases (cont.)
________________ is a method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration.
Section 18-4

46. Reactions Between Acids and Bases (cont.)
In a titration procedure, a measured volume of an acid or base of unknown concentration is placed in a beaker, and initial pH recorded.
A buret is filled with the titrating solution of known concentration, called a ____________.
Section 18-4

47. Reactions Between Acids and Bases (cont.)
Measured volumes of the standard solution are added slowly and mixed into the solution in the beaker, and the pH is read and recorded after each addition. The process continues until the reaction reaches the ______________, which is the point at which moles of H+ ion from the acid equals moles of OH– ion from the base.
An abrupt change in pH occurs at the equivalence point.
Section 18-4

48. Reactions Between Acids and Bases (cont.)
Section 18-4

49. Reactions Between Acids and Bases (cont.)
Chemical dyes whose color are affected by acidic and basic solutions are called __________________
Section 18-4

50. Reactions Between Acids and Bases (cont.)
An __________is the point at which an indicator used in a titration changes color.
An indicator will change color at the equivalence point.
Section 18-4

51. Salt Hydrolysis
In ____________, the anions of the dissociated salt accept hydrogen ions from water or the cations of the dissociated salt donate hydrogen ions to water.
Section 18-4

52. Salt Hydrolysis (cont.)
Salts that produce basic solutions
KF is the salt of a strong base (KOH) and a weak acid (HF).
KF(s) → K+(aq) + F–(aq)
Section 18-4

53. Salt Hydrolysis (cont.)
Salts that produce acidic solutions
NH4Cl is the salt of a weak base (NH3) and strong acid (HCl).
When dissolved in water, the salt dissociates into ammonium ions and chloride ions.
NH4Cl(s) → NH4+(aq) + Cl–(aq)
Section 18-4

54. Salt Hydrolysis (cont.)
Salts that produce neutral solutions
NaNO3 is the salt of a strong acid (HNO3) and a strong base (NaOH).
Little or no salt hydrolysis occurs because neither Na+ nor NO3– react with water.
Section 18-4

55. The pH of blood must be kept in within a narrow range.
Buffered Solutions
The pH of blood must be kept in within a narrow range.
_________ are solutions that resist changes in pH when limited amounts of acid or base are added.
Section 18-4

56. Buffered Solutions (cont.)
Ions and molecules in a buffer solution resist changes in pH by reacting with any hydrogen ions of hydroxide ions added to the buffered solution.
HF(aq) ↔ H+(aq) + F–(aq)
When acid is added, the equilibrium shifts to the left.
Section 18-4

57. Buffered Solutions (cont.)
Additional H+ ions react with F– ions to form undissociated HF molecules but the pH changes little.
The amount of acid or base that a buffer solution can absorb without a significant change in pH is called the _____________
Section 18-4

58. Buffered Solutions (cont.)
A buffer is most effective when the concentrations of the conjugate acid-base pair are equal or nearly equal.
Section 18-4

59. Example Problems:
Write equation for the salt hydrolysis reaction occurring when the following salt dissolves in water. Classify it as acidic, basic or neutral.
Ammonium nitrate

60. A B C D Section 18.4 Assessment
In a neutralization reaction, an acid and base react to form:
A. salt and oxygen gas
B. salt and ammonia
C. salt and water
D. precipitate and water A B C D
Section 18-4

61. A B C D Section 18.4 Assessment
Solutions that resist changes in pH are called ____.
A. titrants
B. salts
C. conjugate pairs
D. buffers A B C D
Section 18-4