1. Acids / Bases

2. Arrhenius Acids Arrhenius acids produce H+ ions in water.
have a sour taste.
turn blue litmus paper red.
corrode some metals.
Citrus fruits are sour because of the presence of acids.

3. Naming Acids
Acids with H and a nonmetal are named with the prefix hydro− and end with −ic acid.
HCl hydrochloric acid
Acids with H and an oxygen-containing polyatomic ion are named by changing the end of the name of the polyatomic ion from −ate to −ic acid or −ite to −ous acid.
ClO3− chlorate HClO3 chloric acid
ClO2− chlorite HClO2 chlorous acid

4. Naming Some Common Acids

5. Learning Check
Select the correct name for each of the following acids.
1. HBr A. bromic acid
B. bromous acid
C. hydrobromic acid
2. H2CO3 A. carbonic acid
B. hydrocarbonic acid
C. carbonous acid
3. HBrO2 A. bromic acid
B. hydrobromous acid
C. bromous acid

6. Solution 1. HBr C. hydrobromic acid
The name of an acid with H and one nonmetal uses the prefix hydro− and ends with −ic acid.
2. H2CO3 A. carbonic acid
An acid with H and a polyatomic ion, bicarbonate, HCO3− is named by changing the end of the ion’s name from −ate to −ic acid.
3. HBrO2 C. bromous acid
This acid of bromite, (BrO2−) is bromous acid.

7. Bases Arrhenius bases produce OH− ions in water.
taste bitter or chalky.
feel soapy and slippery.
turn red litmus paper blue.
turn the phenolphthalein indicator pink.

8. Some Common Bases Bases with OH− ions are named as the hydroxide of
the metal in the formula.
NaOH sodium hydroxide
KOH potassium hydroxide
Ba(OH)2 barium hydroxide
Al(OH)3 aluminum hydroxide
Fe(OH)3 iron (III) hydroxide

9. Learning Check 1. HNO2 A. iodic acid 2. Ca(OH)2 B. sulfuric acid
Match the formulas with the names.
1. HNO2 A. iodic acid
2. Ca(OH)2 B. sulfuric acid
3. H2SO4 C. sodium hydroxide
4. HIO3 D. nitrous acid
5. NaOH E. calcium hydroxide

10. Solution 1. HNO2 D. nitrous acid 2. Ca(OH)2 E. calcium hydroxide
Match the formulas with the names.
1. HNO2 D. nitrous acid
2. Ca(OH)2 E. calcium hydroxide
3. H2SO4 B. sulfuric acid
4. HIO3 A. iodic acid
5. NaOH C. sodium hydroxide

11. Brønsted–Lowry Acids According to the Brønsted–Lowry theory, acids
donate a proton (H+).
In the reaction of hydrochloric acid and water,
HCl is the acid that donates H+, and
H2O is the base that accepts H+.

12. Brønsted–Lowry Bases According to the Brønsted–Lowry theory, bases
accept a proton (H+).
In the reaction of ammonia and water,
NH3 is the base that accepts H+, and
H2O is the acid that donates H+.

13. Conjugate Acid–Base Pairs
In any acid–base reaction, there are two conjugate
acid–base pairs.
Each is related by the loss and gain of H+.
One occurs in the forward direction.
One occurs in the reverse direction.
conjugate acid–base pair 1
conjugate acid–base pair 2

14. Conjugate Acid–Base Pairs

15. Conjugate Acids and Bases, HF
The first conjugate acid–base pair is HF/F−. HF loses one H+ to form its conjugate base F−.
The other conjugate acid–base pair is H2O/H3O+. H2O acts as a base accepting one H+ to form its conjugate acid H3O+.

16. Conjugate Acid–Base Pairs

17. Conjugate Acids and Bases, NH3
The first conjugate acid–base pair is NH3/NH4+. NH3, acts as a base by gaining H+ to form its conjugate acid NH4+.
The other conjugate acid–base pair is H2O/OH–. H2O acts as an acid by donating one H+ to form its conjugate base OH−.

18. Learning Check 1. Write the conjugate base of the following. A. HBr
B. H2S
C. H2CO3
2. Write the conjugate acid of the following.
A. NO2−
B. NH3
C. OH−

19. Solution 1. Write the conjugate base of the following.
Remove H+ to write the conjugate base.
A. HBr Br −
B. H2S HS−
C. H2CO HCO3−
2. Write the conjugate acid of the following.
Add H+ to write the conjugate acid.
A. NO2− HNO2
B. NH3 NH4+
C. OH− H2O

20. Learning Check 1. The conjugate base of HCO3− is
A. CO32−. B. HCO3− C. H2CO3.
2. The conjugate acid of HCO3− is
3. The conjugate base of H2O is
A. OH−. B. H2O C. H3O+.
4. The conjugate acid of H2O is

21. Solution 1. (A) The conjugate base of HCO3− is, CO32−.
2. (C) The conjugate acid of HCO3− is H2CO3.
3. (A) The conjugate base of H2O is OH−.
4. (C) The conjugate acid of H2O is H3O+.

22. Learning Check
Identify the acid–base conjugate pairs.

23. Solution Identify the acid–base conjugate pairs.
conjugate acid–base pair
conjugate acid–base pair
conjugate acid–base pair
conjugate acid–base pair
conjugate acid–base pair
conjugate acid–base pair

24. Strengths of Acids
Strong acids completely ionize (100%) in aqueous solutions. We use a single arrow in the chemical equation.
HCl(g) + H2O(l) H3O+(aq) + Cl−(aq)
Weak acids dissociate only slightly in water to form a solution of mostly molecules and a few ions.
H2CO3(aq) + H2O(l) H3O+(aq) + HCO3−(aq)

25. Strong and Weak Acids There are six strong acids in solution.
HCl, a strong acid, dissociates 100%.
Acetic acid (CH3COOH), a weak acid, is mostly molecules and only a few ions.

26. Stronger Acid, Weaker Conjugate Base
Weaker acids have a varying degree of strength. The stronger the acid, the weaker the conjugate base.

27. Stronger Acid, Weaker Conjugate Base
Weak acids
make up most of the acids and
have strong conjugate bases.
Increasing Base Strength
Increasing Acid Strength

28. H2CO3, Weak Acid H2CO3 is a diprotic acid. It partially dissociates in
water, giving up one H+ at a time.
H2CO3(aq) + H2O(l) H3O+(aq) + HCO3−(aq)
Because HCO3− is also a weak acid, a second
dissociation can take place to produce another
hydronium ion and the carbonate ion.
HCO3−(aq) + H2O(l) H3O+(aq) + CO32−(aq)

29. H2SO4, Strong Acid
H2SO4 is also a diprotic acid. It completely dissociates
in water.
H2SO4 (aq) + H2O(l) H3O+(aq) + HSO4−(aq)
Because HSO4− is a weak acid, a second dissociation
takes place to produce another hydronium ion and the
sulfate ion.
HSO4−(aq) + H2O(l) H3O+(aq) + SO42−(aq)

30. Strong Bases Strong bases
are formed from metals of Groups 1A(1) and 2A(2).
include LiOH, NaOH, KOH, and Ca(OH)2.
dissociate completely in water.
KOH(s) K+(aq) + OH−(aq)

31. Weak Bases Weak bases are most other bases.
dissociate only slightly in water.
form only a few ions in water.
NH3(g) + H2O(l) NH4+(aq) + OH−(aq)

32. Learning Check
Identify each of the following as a strong or weak acid or base.
A. HBr
B. HNO2
C. NaOH
D. H2SO4
E. Cu(OH)2

33. Solution
Identify each of the following as a strong or weak acid or base.
A. HBr strong acid
B. HNO2 weak acid
C. NaOH strong base
D. H2SO4 strong acid
E. Cu(OH) weak base

34. Acid Dissociation Constant, Ka
In a weak acid, the rate of the dissociation of the acid is equal to the rate of the association.
HA + H2O H3O+ + A–
The equilibrium expression is indicated below.

35. Ka, Formic Acid
Formic acid, HCHO2, the acid found in bee and ant stings, is a weak acid.
The equilibrium expression is indicated below

36. Acid Characteristics and Ka

37. Some Acid Dissociation Constants
Ka values for some weak acids are shown in Table 10.4.

38. Writing Ka for a Weak Acid
Write the Ka for H2S.
1. Write the equation for the dissociation of H2S.
2. Set up the Ka expression.

39. Learning Check
Write the Ka for hypochlorous acid, HClO.

40. Solution Write the Ka for hypochlorous acid, HClO.
1. Write the equation for the dissociation of the weak acid, HClO.
2. Set up the Ka expression.

41. Ionization of Water In the ionization of water,
H+ is transferred from one H2O molecule to another.
one water molecule acts as an acid, while another acts as a base.

42. Ion Product of Water, Kw
The ion product constant, Kw, for water at 25 °C
is the product of the concentrations of the hydronium and hydroxide ions.
is obtained from the concentrations in pure water.

43. Pure Water is Neutral
In pure water, the ionization of water molecules produces small but equal quantities of H3O+ and OH− ions.

44. Acidic Solutions Adding an acid to pure water increases the [H3O+],
decreases the [OH−], and
causes the [H3O+] to
exceed 1.0 x 10−7 M.

45. Basic Solutions Adding a base to pure water, increases the [OH−],
decreases the [H3O+], and
causes the [OH−] to exceed 1.0 x 10−7 M.

46. Comparison of [H3O+] and [OH−]

47. [H3O+] and [OH−] in Solutions
In neutral, acidic, or basic solutions, the Kw at 25 °C is
always 1.0 x 10−14.

48. Guide to Calculating [H3O+] and [OH−]

49. Calculating [H3O+]
What is the [H3O+] of a solution if [OH−] is 5.0 x 10−8 M?
Step 1 Write the Kw for water.
Step 2 Solve the Kw for the unknown [H3O+].
Step 3 Substitute the known [OH−] into the equation
and calculate.

50. pH Scale The pH of a solution
is used to indicate the acidity of a solution.
has values that range from 0 to 14 representing the H3O+ concentration of a solution.
is acidic when the values are less than 7.
is neutral with a pH of 7.
is basic when the values are greater than 7.

51. Calculating pH pH is the negative logarithm (base 10) of the [H3O+] .
For a solution with [H3O+] = 1 x 10−4 M:

52. Learning Check
The [H3O+] of tomato juice is 2 x 10−4 M. What is the pH of the solution?
A. 4.0
B. 3.7
C. 10.3

53. Learning Check A. pH = 9.0 B. pH = 7.0 C. pH = 5.0
What is the pH of coffee if the [H3O+] is 1 x 10−5 M?
A. pH = 9.0
B. pH = 7.0
C. pH = 5.0

54. Learning Check
The [OH−] of a solution is 1.0 x 10−3 M. What is the pH? A B
C. –11.00

55. [H3O+], [OH-], and pH Values

56. Buffers A buffer solution
maintains pH by neutralizing added acid or base.
in the body, absorbs H3O+ or OH− from foods and cellular processes to maintain pH.

57. Buffers (continued) When an acid or base is added
to water, the pH changes drastically.
to a buffer solution, the pH does not change very much; pH is maintained.