1. Acids, Bases and Salts Chapter 15
Hein and Arena
Eugene Passer Chemistry Department Bronx Community College
© John Wiley and Sons, Inc
Version 2.0
12th Edition

2. Chapter Outline 15.1 Acids and Bases 15.8 Ionization of Water
15.2 Reactions of Acids
15.9 Introduction to pH
15.3 Reactions of Bases
Neutralization
15.4 Salts
Writing Net Ionic Equations
15.5 Electrolytes and Nonelectrolytes
Acid Rain
15.6 Dissociation and Ionization of Electrolytes
Colloids
15.7 Strong and Weak Electrolytes
Properties of Colloids

3. 15.1 Acids and Bases

4. Acid Properties sour taste change the color of litmus from blue to red
react with
metals such as zinc and magnesium to produce hydrogen gas
hydroxide bases to produce water and an ionic compound (salt)
carbonates to produce carbon dioxide.
These properties are due to the release of hydrogen ions, H+, into water solution.

5. Base Properties bitter or caustic taste a slippery, soapy feeling.
the ability to change litmus red to blue
the ability to interact with acids

6. Svante Arrhenius was a Swedish scientist who lived from 1859-1927.
In 1884 he advanced a theory of acids and bases.

7. An Arrhenius acid “is a hydrogen-containing substance that dissociates to produce hydrogen ions.”
HA → H+ + A-
acid

8. An Arrhenius base is a hydroxide-containing substance that dissociates to produce hydroxide ions in aqueous solution.
MOH → M+(aq) + OH-(aq)
base

9. An Arrhenius acid solution contains an excess of H+ ions.
An Arrhenius base solution contains an excess of OH- ions.

10. J. N. Bronsted (1897-1947) was a Danish chemist and T. M
J.N. Bronsted ( ) was a Danish chemist and T. M. Lowry ( ) was an English chemist.
In 1923 they advanced their theory of acids and bases.

11. A Bronsted-Lowry acid is a proton (H+) donor.
A Bronsted-Lowry base is a proton (H+) acceptor.

12. HCl + H2O(l) → H3O+(aq) + Cl-(aq)
Bronsted-Lowry Acid
proton acceptor
Bronsted-Lowry Base
proton donor
HCl + H2O(l) → H3O+(aq) + Cl-(aq)

13. hydrogen ion does not exist in water a hydronium ion is formed
hydrogen ion combines with water

14. Conjugate acid-base pairs differ by a proton.
When an acid donates a proton it becomes the conjugate base.
HCl(g) →
Cl-(aq)
acid
base

15. Conjugate acid-base pairs differ by a proton.
When a base accepts a proton it becomes the conjugate acid.
H2O (l) →
H3O+(aq)
base
acid

16. Conjugate acid-base pairs differ by a proton.
HCl(g) + →
Cl-(aq)
H3O+(aq)
H2O (l)
acid
base

17. Conjugate acid-base pairs differ by a proton.
HCl(g) + →
Cl-(aq)
H3O+(aq)
H2O (l)
acid
base

18. In 1923 G. N. Lewis developed a more comprehensive theory of acids and bases.
The Lewis theory deals with the way in which a substance with an unshared pair of electrons reacts in an acid-base type of reaction.

19. A Lewis acid is an electron-pair acceptor.
A Lewis base is an electron-pair donor.

20. Electron Pair Acceptor
Lewis Acid
Electron Pair Acceptor
Electron pair donated to H+
Lewis Base
Electron Pair Donor

21. Electron Pair Acceptor
Lewis Acid
Electron Pair Acceptor
Electron pair donated to B
Lewis Base
Electron Pair Donor

23. 15.2 Reactions of Acids

24. In aqueous solution, the H+ or H3O+ ions are responsible for the characteristic reactions of acids.

25. acid + metal → hydrogen + ionic compound
Reaction with Metals Acids react with metals that lie above hydrogen in the activity series of elements to produce hydrogen and an ionic compound (salt):
acid + metal → hydrogen + ionic compound
2HCl(aq) + Ca(s) → H2(g) + CaCl2(aq)
H2SO4(aq) + Mg(s) → H2(g) + MgSO4(aq)

26. 3Zn(s) + 8HNO3(dilute) → 3Zn(NO3)2 (aq) + 2NO(g) + 4H2O(l)
Reaction with Metals Oxidizing acids react with metals to produce water instead of hydrogen:
3Zn(s) + 8HNO3(dilute) → 3Zn(NO3)2 (aq) + 2NO(g) + 4H2O(l)

27. Reaction with Bases The reaction of an acid with a base is called a neutralization reaction. In an aqueous solution the products are a salt and water:
HBr(aq) + KOH(aq) → KBr(aq) + H2O(l)
acid
base
salt
2HNO3(aq) + Ca(OH)2(aq) → Ca(NO3)2(aq) + 2H2O(l)
acid
base
salt

28. Reaction with Metal Oxides In an aqueous solution the products are a salt and water. This type of reaction is closely related to that of an acid with a base:
2HCl(aq) + Na2O(s) → 2NaCl(aq) + H2O(l)
acid
metal oxide
salt
H2SO4(aq) + MgO(s) → MgSO4(aq) + H2O(l)
acid
salt
metal oxide

29. Reaction with Carbonates Most acids react with carbonates to produce carbon dioxide, water and an ionic compound:
2HCl(aq) + Na2CO3(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
acid
carbonate
salt
H2SO4(aq) + MgCO3(s) → MgSO4(aq) + H2O(l) + CO2(g)
acid
carbonate
salt
HCl(aq) + NaHCO3(aq) → NaCl(aq) + H2O(l) + CO2(g)
acid
carbonate
salt

30. Carbonic acid (H2CO3) is not the product when an acid reacts with a carbonate because carbonate spontaneously decomposes into carbon dioxide and water.
H2CO3(aq) → CO2(g) + H2O(l)

31. 15.3 Reactions of Bases

32. Reaction with Acids The reaction of an acid with a base is called a neutralization reaction. In an aqueous solution the products are a salt and water:
HBr(aq) + KOH(aq) → KBr(aq) + H2O(l)
acid
base
salt
2HNO3(aq) + Ca(OH)2(aq) → Ca(NO3)2(aq) + 2H2O(l)
acid
base
salt

33. Amphoteric Hydroxides Hydroxides of certain metals are amphoteric, meaning they are capable of reacting as either an acid or a base:
Zn(OH)2 + 2HCl(aq) → ZnCl2(aq) + 2H2O(l)
base
acid
salt
Zn(OH)2 + 2KOH(aq) → K2Zn(OH)4(aq)
Lewis acid
base

34. Reaction of NaOH and KOH with Certain Metals Some amphoteric metals react directly with the strong bases sodium hydroxide and potassium hydroxide to produce hydrogen:
base + metal + water → salt + hydrogen
2KOH(aq) + 2Al(s) + 6H2O(l) → 2KAl(OH)4(aq) + 3H2(g)
Lewis acid
2NaOH(aq) + Zn(s) + 2H2O(l) → Na2Zn(OH)4(aq) + H2(g)
Lewis acid

35. 15.4 Salts

36. Salts can be considered compounds derived from acids and bases
Salts can be considered compounds derived from acids and bases. They consist of positive metal or ammonium ions combined with nonmetal ions (OH- and O2- excluded).
Salts are usually crystalline and have high melting and boiling points.
Chemists use the terms ionic compound and salt interchangeably.

37. Salt Formation NaOH HCl NaCl
The negative ion of the salt is derived from the acid.
The positive ion of the salt is derived from the base.
NaOH
HCl
base
acid
NaCl
salt

38. 15.5 Electrolytes and Nonelectrolytes

39. Nonelectrolytes are substances whose aqueous solutions do not conduct electricity.
Electrolytes are substances whose aqueous solutions conduct electricity.
Nonelectrolytes are not capable of producing ions in solution.
Electrolytes are capable of producing ions in solution.

40. Classes of compounds that are electrolytes are:
acids
bases
salts
solutions of oxides that form an acid or a base

42. 15.6 Dissociation and Ionization of Electrolytes

43. Dissociation is the process by which the ions of a salt separate as the salt dissolves.

44. In a crystal of sodium chloride positive sodium ions are bonded to negative chloride ions.
15.2

45. In aqueous solution the sodium and chloride ions dissociate from each other.
15.2

46. In aqueous solution the sodium and chloride ions dissociate from each other.
15.2

47. Na+ and Cl- ions hydrate with H2O molecules.
15.2

48. The equation representing the dissociation of NaCl is:
NaCl(s) + (x+y)H2O → Na+(H2O)x + Cl-(H2O)y
The equation can be written more simply as:
NaCl(s) → Na+(aq) + Cl-(aq)

49. Ionization is the formation of ions.
Ionization occurs as the result of a chemical reaction of certain substances with water.
Ionization is the formation of ions.

50. Acetic acid ionizes in water to form acetate ion and hydronium ion.
HC2H3O2 + H2O H3O+ + C2H3O2- →
Lewis acid
Lewis base
The equation can be written more simply as:
HC3H3O2 H+ + C2H3O2- →
In the absence of water, ionization reactions do not occur.

51. 15.7 Strong and Weak Electrolytes

52. Weak Electrolyte An electrolyte that is ionized to a small extent in aqueous solution.
Strong Electrolyte An electrolyte that is essentially 100% ionized in aqueous solution.

53. Most salts are strong electrolytes
Strong acids and bases (highly ionized) are strong electrolytes.
Weak acids and bases (slightly ionized) are weak electrolytes.

54. 1% ionized 100% ionized Strong Acid Weak Acid HCl Solution
HC2H3O2 Solution
15.3

55. HC2H3O2(aq) → H+ (aq) + C2H3O2(aq)
Both the ionized and unionized forms of a weak electrolyte are present in aqueous solution.
HC2H3O2(aq) → H+ (aq) + C2H3O2(aq) →
ionized
unionized

56. HNO3, a strong acid, is 100 % dissociated. HNO3(aq) → H+(aq) + NO3(aq)
HNO2, a weak acid, is only slightly ionized.
HNO2(aq) → H+(aq) + NO2(aq) →

58. NaOH → Na+(aq) + OH-(aq)
Electrolytes yield two or more ions per formula unit upon dissociation.
NaOH → Na+(aq) + OH-(aq)
two ions in solution per formula unit
Na2SO4 → 2Na+(aq) + SO4-(aq)
three ions in solution per formula unit
Fe2(SO4 )3 → 2Fe3+(aq) + 3SO4-(aq)
five ions in solution per formula unit

59. NaOH → Na+(aq) + OH-(aq)
Electrolytes yield two or more moles of ions per mole of electrolyte upon dissociation.
NaOH → Na+(aq) + OH-(aq)
1 mole
Na2SO4 → 2Na+(aq) + SO4-(aq)
1 mole
2 moles
Fe2(SO4 )3 → 2Fe3+(aq) + 3SO4-(aq)
1 mole
2 moles
3 moles

60. Colligative Properties of Electrolyte Solutions

61. NaOH → Na+(aq) + OH-(aq)
Substances that form ions in aqueous solutions change the colligative properties of water in proportion to the number of ions formed.
NaOH → Na+(aq) + OH-(aq)
1 mole
Two moles of ions will depress the freezing point of water twice that of one mole of a nonelectrolyte.
Fe2(SO4 )3 → 2Fe3+(aq) + 3SO4-(aq)
1 mole
2 moles
3 moles
Five moles of ions will depress the freezing point of water five times that of one mole of a nonelectrolyte.

62. 15.8 Ionization of Water

63. → H2O + H2O → H3O+ + OH- → H2O → H+ + OH- Water ionizes slightly.
hydroxide ion
hydronium ion
acid
base
H2O + H2O → H3O+ + OH- →
Water ionization can be expressed more simply as:
H2O → H+ + OH- →
[H3O+] or [H+] = 1.0 x 10-7 mol/L
[OH-] = 1.0 x 10-7 mol/L
Two out of every 1 billion water molecules are ionized.

64. 15.9 Introduction to pH

65. pH is the negative logarithm of the hydrogen ion concentration.
pH = -log[H+]

66. Calculation of pH

67. pH = -log[H+] [H+] = 1 x 10-5 when this number is exactly 1
pH = this number without the minus sign.
when this number is exactly 1
pH = 5

68. one significant figure
pH = -log[H+]
[H+] = 2 x 10-5
when this number is between 1 and 10
one significant figure
ph = 4.7
pH is between this number and the next lower number (between 4 and 5).
one decimal place
The number of decimal places of a logarithm is equal to the number of significant figures in the original number.

69. What is the pH of a solution with an [H+] of 1.0 x 10-11?
2 significant figures
pH = - log(1.0 x 10-11)
pH = 11.00
2 decimal places

70. log[H+] = log (6.0 x 10-4) = -3.22 pH = - log[H+] = -(3.22) = 3.22
What is the pH of a solution with an [H+] of 6.0 x 10-4?
2 significant figures
log[H+] = log (6.0 x 10-4) = -3.22
pH = - log[H+] = -(3.22) = 3.22
2 decimal places

71. log[H+] = log(5.47 x 10-8) = -7.262 pH = - log[H+] = -(7.262) = 7.262
What is the pH of a solution with an [H+] of 5.47 x 10-8?
3 significant figures
log[H+] = log(5.47 x 10-8) =
pH = - log[H+] = -(7.262) = 7.262
3 decimal places

72. The pH scale of Acidity and Basicity
15.4

73. 15.10 Neutralization

74. HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
Neutralization The reaction of an acid and a base to form a salt and water.
HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
acid
base
salt

75. Titrations

76. Titration The process of measuring the volume of one reagent required to react with a measured mass or volume of another reagent.

77. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
42.00 mL of M NaOH solution is required to neutralize mL of hydrochloric acid solution. What is the molarity of the acid solution?
Convert mL of NaOH to liters of NaOH
The equation for the reaction is
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
acid
base
salt
Calculate the liters of NaOH that react.
The unit of volume when using molarity is liters.
Calculate the moles of NaOH that react.

78. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
42.00 mL of M NaOH solution is required to neutralize mL of hydrochloric acid solution. What is the molarity of the acid solution.
The equation for the reaction is
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
acid
base
salt
The moles of NaOH that react equals the moles of HCl that react.
The mole ratio of HCl to NaOH is 1:1
mol NaOH react.
mol HCl react.
The molarity of the HCl solution is

79. 15.11 Writing Net Ionic Equations

80. HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
In the formula equation all compounds are written using their molecular or formula expressions.
HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
acid
base
salt
In the total ionic equation all ions present in solution are written.
(H+ + Cl-) + (K+ + OH-) → K+ + Cl- + H2O
In the net ionic equation only the ions that react are written.
Ions that do not participate in a chemical reaction are called spectator ions.
Cl- ion does not react.
K+ ion does not react.
H+(aq) + OH-(aq) → H2O(l)

81. Rules for Writing Equations
Strong electrolytes in solution are written in their ionic form.
Weak electrolytes are written in their molecular form.
Nonelectrolytes are written in their molecular form.

82. Insoluble substances, precipitates and gases are written in their molecular forms.
The net ionic equation should include only substances that have undergone a chemical change. Spectator ions are omitted from the net ionic equation.
Equations must be balanced both in atoms and in electrical charge.

83. Examples

84. formula equation total ionic equation net ionic equation
2AgNO3(aq) + BaCl2(aq) → 2AgCl(s) + Ba(NO3)2(aq)
formula equation
spectator ions
(2Ag ) + (Ba2+ + 2Cl-) → 2AgCl(s) + (Ba )
total ionic equation
precipitate
Ag+ + Cl- → AgCl(s)
net ionic equation

85. formula equation total ionic equation net ionic equation
spectator ions
total ionic equation
gas
net ionic equation

86. formula equation total ionic equation net ionic equation
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
formula equation
spectator ion
Mg(s) + (2H+ + 2Cl-) → (Mg2+ + 2Cl-)+ H2(g)
total ionic equation
Electrical charge on both sides of the equation = +2
Mg + 2H+ → Mg2+ + H2(g)
net ionic equation

87. 15.12 Acid Rain

88. The increase in acidity might be from natural or industrial sources.
Acid rain is any atmospheric precipitation that is more acidic than usual.
The increase in acidity might be from natural or industrial sources.

89. CO2(g) + H2O(l) H2CO3(aq) H+ + HCO3
The pH of rain is lower in the eastern US and higher in the western US.
Unpolluted rain has a pH of 5.6 because of carbonic acid formation in the atmosphere.
CO2(g) + H2O(l) H2CO3(aq) H+ + HCO3 →

90. Process of Acid Rain Formation
emission of nitrogen and sulfur oxides into the air
transportation of these oxides into the atmosphere
chemical reactions between the oxides and water forming sulfuric acid (H2SO4) and nitric acid (HNO3)
rain or snow, which carries the acids to the ground
From the burning of fossil fuels.

91. Effects of Acid Rain
freshwater plants and animals decline significantly when rain is acidic
aluminum is leached from the soil into lakes and adversely affects fish gills.
the waxy protective coat on plants is dissolved making them vulnerable to bacteria and fungal attack

92. Effects of Acid Rain
it is responsible for extensive and continuing damage to buildings, monuments and statues
it reduces the durability of paint and promotes the deterioration of paper, leather and cloth

93. 15.13 Colloids

94. Colloid A dispersion in which the dispersed particles are larger than the solute ions or molecules of a true solution and smaller than the particles of a mechanical suspension.

95. Colloid is derived from the Greek word “kolla” meaning “glue.”
The term colloid does not imply a system has a gluelike quality.

96. The fundamental difference between a colloidal dispersion and a true solution is the size of the particles.
In ordinary solutions the size of solute particles range from 0.1 to 1 nm.
The size of colloidal particles range from 1 to 1,000 nm.
In a solution the particles are usually single ions or molecules.
In a colloid the particles are usually aggregations of ions or molecules.

98. 15.14 Properties of Colloids

99. In 1827 Robert Brown illuminated an aqueous suspension of pollen under a high powered microscope.
He observed a trembling erratic motion of the pollen grains.
This erratic motion is characteristic of colloids in general.
This random motion is called Brownian movement.

100. The Tyndall effect occurs because colloidal particles are large enough to scatter light.
When an intense beam of light is passed through an ordinary solution and viewed at an angle, the beam passing through the solution is hardly visible.
A beam of light is clearly visible and sharply outlined when it is passed through a colloidal dispersion.
This phenomenon is known as the Tyndall effect.

101. Colloidal particles have huge surface areas in comparison to the volume of the same particles if they were aggregated into one large particle.
Colloidal particles become electrically charged when they adsorb ions on their surfaces.
This occurs because surface atoms or ions of the colloid attract and adsorb ions or polar molecules from the dispersion medium.

102. The End