Chemistry Third Edition Julia Burdge Lecture Power Points
Chemistry Third Edition Julia Burdge Lecture Power. Points Chapter 16 Acids and Bases Copyright © 2012, The Mc. Graw Hill Compaies, Inc. Permission required for reproduction or display.
CHAPTER 16. 1 16. 2 16. 3 16. 4 16. 5 16. 6 16. 7 16. 8 16. 9 16 Acids and Bases Brønsted Acids and Bases The Acid Base Properties of Water The p. H Scale Strong Acids and Bases Weak Acids and Acid Ionization Constants Weak Bases and Base Ionization Constants Conjugate Acid Base Pairs Diprotic and Polyprotic Acids Molecular Structure and Acid Strength 2
CHAPTER 16 Acids and Bases 16. 10 Acid Base Properties of Salt Solutions 16. 11 Acid Base Properties of Oxides and Hydroxides 16. 12 Lewis Acids and Bases 3
16. 1 Brønsted Acids and Bases Topics Brønsted Acids and Bases 4
16. 1 Brønsted Acids and Bases A Brønsted acid is a substance that can donate a proton and a Brønsted base is a substance that can accept a proton. 5
16. 1 Brønsted Acids and Bases 6
16. 1 Brønsted Acids and Bases 7
16. 1 Brønsted Acids and Bases 8
16. 1 Brønsted Acids and Bases 9
SAMPLE PROBLEM 16. 1 What is (a) the conjugate base of HNO 3, (b) the conjugate acid of O 2–, (c) the conjugate base of HSO 4– , and (d) the conjugate acid of HCO 3– ? Strategy To find the conjugate base of a species, remove a proton from the formula. To find the conjugate acid of a species, add a proton to the formula. 10
SAMPLE PROBLEM 16. 1 What is (a) the conjugate base of HNO 3, (b) the conjugate acid of O 2–, (c) the conjugate base of HSO 4– , and (d) the conjugate acid of HCO 3– ? Solution 11
16. 2 The Acid Base Properties of Water Topics The Acid Base Properties of Water 12
16. 2 The Acid Base Properties of Water A species that can behave either as a Brønsted acid or a Brønsted base is called amphoteric. This reaction is known as the autoionization of water. 13
16. 2 The Acid Base Properties of Water In pure water at 25 °C: 14
16. 2 The Acid Base Properties of Water The relative amounts of H 3 O+ and OH– determine whether a solution is neutral, acidic, or basic. • When [H 3 O+] = [OH–], the solution is neutral. • When [H 3 O+] > [OH–], the solution is acidic. • When [H 3 O+] < [OH–], the solution is basic. 15
SAMPLE PROBLEM 16. 3 The concentration of hydronium ions in stomach acid is 0. 10 M. Calculate the concentration of hydroxide ions in stomach acid at 25°C. Strategy Use the value of Kw to determine [OH–] when [H 3 O+] = 0. 10 M. Setup 16
SAMPLE PROBLEM 16. 3 Solution 17
16. 3 The p. H Scale Topics The p. H Scale 18
16. 3 The p. H Scale Because [H 3 O+] = [OH–] = 1. 0 × 10– 7 M in pure water at 25°C, the p. H of pure water at 25°C is –log (1. 0 × 10– 7) = 7. 00 19
16. 3 The p. H Scale Remember, too, that a solution in which [H 3 O+] = [OH–] is neutral. At 25°C, therefore, a neutral solution has p. H 7. 00. An acidic solution, one in which [H 3 O+] > [OH–], has p. H < 7. 00, whereas a basic solution, in which [H 3 O+] < [OH–], has p. H > 7. 00. 20
16. 3 The p. H Scale 21
16. 3 The p. H Scale 22
16. 3 The p. H Scale A measured p. H can be used to determine experimentally the concentration of hydronium ion in solution. 23
SAMPLE PROBLEM 16. 4 Determine the p. H of a solution at 25°C in which the hydronium ion concentration is (a) 3. 5 × 10– 4 M, (b) 1. 7 × 10– 7 M, and (c) 8. 8 × 10– 11 M. Setup 24
SAMPLE PROBLEM 16. 4 Solution 25
SAMPLE PROBLEM 16. 5 Calculate the hydronium ion concentration in a solution at 25°C in which the p. H is (a) 4. 76, (b) 11. 95, and (c) 8. 01. Setup Solution 26
16. 3 The p. H Scale A p. OH scale analogous to the p. H scale can be defined using the negative base 10 logarithm of the hydroxide ion concentration of a solution, [OH–]. 27
16. 3 The p. H Scale 28
16. 3 The p. H Scale 29
SAMPLE PROBLEM 16. 6 Determine the p. OH of a solution at 25°C in which the hydroxide ion concentration is (a) 3. 7 × 10– 5 M, (b) 4. 1 × 10– 7 M, and (c) 8. 3 × 10– 2 M. Setup 30
SAMPLE PROBLEM 16. 6 Solution 31
SAMPLE PROBLEM 16. 7 Calculate the hydroxide ion concentration in a solution at 25°C in which the p. OH is (a) 4. 91, (b) 9. 03, and (c) 10. 55. Setup 32
SAMPLE PROBLEM 16. 7 Solution 33
16. 4 Strong Acids and Bases Topics Strong Acids Strong Bases 34
16. 4 Strong Acids and Bases Strong Acids The ionization of strong acids and the dissociation of strong bases generally are not treated as equilibria but rather as processes that go to completion. This makes the determination of p. H for a solution of strong acid or strong base relatively simple. 35
16. 4 Strong Acids and Bases Strong Acids Remember that although sulfuric acid has two ionizable protons, only the first ionization is complete. It is a good idea to commit this short list of strong acids to memory. 36
16. 4 Strong Acids and Bases Strong Acids Because the ionization of a strong acid is complete, the concentration of hydronium ion at equilibrium is equal to the starting concentration of the strong acid. 37
SAMPLE PROBLEM 16. 8 Calculate the p. H of an aqueous solution at 25°C that is (a) 0. 035 M in HI, (b) 1. 2 × 10– 4 M in HNO 3, and (c) 6. 7 × 10– 5 M in HCl. O 4. Strategy HI, HNO 3, and HCl. O 4 are all strong acids, so the concentration of hydronium ion in each solution is the same as the stated concentration of the acid. 38
SAMPLE PROBLEM 16. 8 Setup Solution 39
SAMPLE PROBLEM 16. 9 Calculate the concentration of HCl in a solution at 25°C that has p. H (a) 4. 95, (b) 3. 45, and (c) 2. 78. Setup 40
SAMPLE PROBLEM 16. 9 Solution 41
16. 4 Strong Acids and Bases Strong Bases The list of strong bases is also fairly short. It consists of the hydroxides of alkali metals (Group 1 A) and the hydroxides of the heaviest alkaline earth metals (Group 2 A). The dissociation of a strong base is, for practical purposes, complete. 42
16. 4 Strong Acids and Bases Strong Bases Group 1 A Hydroxides Group 2 A Hydroxides 43
16. 4 Strong Acids and Bases Strong Bases As with strong acids, because the reaction goes to completion, the p. H of a strong base solution is relatively easy to calculate. 44
SAMPLE PROBLEM 16. 10 Calculate the p. OH of the following aqueous solutions at 25°C: (a) 0. 013 M Li. OH, (b) 0. 013 M Ba(OH)2, (c) 9. 2 × 10– 5 M KOH. Strategy Li. OH, Ba(OH)2, and KOH are all strong bases. Use reaction stoichiometry to determine hydroxide ion concentration and to determine p. OH. 45
SAMPLE PROBLEM 16. 10 Setup (a) The hydroxide ion concentration is simply equal to the concentration of the base. Therefore, [OH–] = [Li. OH] = 0. 013 M. (b) The hydroxide ion concentration is twice that of the base: Therefore, [OH–] = 2 × [Ba(OH)2] = 2(0. 013 M) = 0. 026 M. (c) The hydroxide ion concentration is equal to the concentration of the base. Therefore, [OH–] = [KOH] = 9. 2 × 10– 5 M. 46
SAMPLE PROBLEM 16. 10 Solution 47
SAMPLE PROBLEM 16. 11 An aqueous solution of a strong base has p. H 8. 15 at 25°C. Calculate the original concentration of base in the solution (a) if the base is Na. OH and (b) if the base is Ba(OH)2. 48
SAMPLE PROBLEM 16. 11 Strategy Use to convert from p. H to p. OH and to determine the hydroxide ion concentration. Consider the stoichiometry of dissociation in each case to determine the concentration of the base itself. 49
SAMPLE PROBLEM 16. 11 Setup (a) The dissociation of 1 mole of Na. OH produces 1 mole of OH–. Therefore, the concentration of the base is equal to the concentration of hydroxide ion. (b) The dissociation of 1 mole of Ba(OH)2 produces 2 moles of OH–. Therefore, the concentration of the base is only one half the concentration of hydroxide ion. 50
SAMPLE PROBLEM 16. 11 Solution 51
16. 5 Weak Acids and Acid Ionization Constants Topics The Ionization Constant, Ka Calculating p. H from Ka Percent Ionization Using p. H to Determine Ka 52
16. 5 Weak Acids and Acid Ionization Constants The Ionization Constant, Ka Most acids are weak acids, which ionize only to a limited extent in water. At equilibrium, an aqueous solution of a weak acid contains a mixture of aqueous acid molecules, hydronium ions, and the corresponding conjugate base. The degree to which a weak acid ionizes depends on the concentration of the acid and the equilibrium constant for the ionization. 53
16. 5 Weak Acids and Acid Ionization Constants The Ionization Constant, Ka Ka is called the acid ionization constant. Although all weak acids ionize less than 100 percent, they vary in strength 54
16. 5 Weak Acids and Acid Ionization Constants The Ionization Constant, Ka The magnitude of Ka indicates how strong a weak acid is. A large Ka value indicates a stronger acid, whereas a small Ka value indicates a weaker acid. 55
16. 5 Weak Acids and Acid Ionization Constants The Ionization Constant, Ka 56
16. 5 Weak Acids and Acid Ionization Constants Calculating p. H from Ka 57
16. 5 Weak Acids and Acid Ionization Constants Calculating p. H from Ka 58
16. 5 Weak Acids and Acid Ionization Constants Calculating p. H from Ka 59
16. 5 Weak Acids and Acid Ionization Constants Calculating p. H from Ka This shortcut gives a good approximation as long as the magnitude of x is significantly smaller than the initial acid concentration. As a rule, it is acceptable to use this shortcut if the calculated value of x is less than 5 percent of the initial acid concentration. This is the formula for the percent ionization of the acid. 60
SAMPLE PROBLEM 16. 12 The Ka of hypochlorous acid (HCl. O) is 3. 5 × 10– 8. Calculate the p. H of a solution at 25°C that is 0. 0075 M in HCl. O. Setup 61
SAMPLE PROBLEM 16. 12 Setup Solution 62
SAMPLE PROBLEM 16. 12 Solution 63
16. 5 Weak Acids and Acid Ionization Constants Percent Ionization 64
SAMPLE PROBLEM 16. 13 Determine p. H and percent ionization for acetic acid solutions at 25°C with concentrations (a) 0. 15 M, (b) 0. 015 M, and (c) 0. 0015 M. Setup Ka for acetic acid is 1. 8 × 10– 5. 65
SAMPLE PROBLEM 16. 13 Solution 66
SAMPLE PROBLEM 16. 13 Solution 67
16. 5 Weak Acids and Acid Ionization Constants Using p. H to Determine Ka Suppose we want to determine the Ka of a weak acid (HA) and we know that a 0. 25 M solution of the acid has a p. H of 3. 47 at 25°C. [H 3 O+] = 10– 3. 47 = 3. 39 × 10– 4 M 68
SAMPLE PROBLEM 16. 14 Aspirin (acetylsalicylic acid, HC 9 H 7 O 4) is a weak acid. It ionizes in water according to the equation A 0. 10 M aqueous solution of aspirin has a p. H of 2. 27 at 25°C. Determine the Ka of aspirin. 69
SAMPLE PROBLEM 16. 14 Setup Solution 70
16. 6 Weak Bases and Base Ionization Constants Topics The Ionization Constant, Kb Calculating p. H from Kb Using p. H to Determine Kb 71
16. 6 Weak Bases and Base Ionization Constants The Ionization Constant, Kb Just as most acids are weak, most bases are also weak. The ionization of a weak base is incomplete and is treated in the same way as the ionization of a weak acid. 72
16. 6 Weak Bases and Base Ionization Constants The Ionization Constant, Kb 73
16. 6 Weak Bases and Base Ionization Constants The Ionization Constant, Kb 74
16. 6 Weak Bases and Base Ionization Constants Calculating p. H from Kb Solving problems involving weak bases requires the same approach we used for weak acids. It is important to remember, though, that solving for x in a typical weak base problem gives us the hydroxide ion concentration rather than the hydronium ion concentration. 75
SAMPLE PROBLEM 16. 15 What is the p. H of a 0. 040 M ammonia solution at 25°C? Setup Solution 76
SAMPLE PROBLEM 16. 15 Solution 77
SAMPLE PROBLEM 16. 15 Solution 78
16. 6 Weak Bases and Base Ionization Constants Using p. H to Determine Kb Just as we can use p. H to determine the Ka of a weak acid, we can also use it to determine the Kb of a weak base. 79
SAMPLE PROBLEM 16. 16 Caffeine, the stimulant in coffee and tea, is a weak base that ionizes in water according to the equation A 0. 15 M solution of caffeine at 25°C has a p. H of 8. 45. Determine the Kb of caffeine. 80
SAMPLE PROBLEM 16. 16 Setup Solution 81
16. 7 Conjugate Acid Base Pairs Topics The Strength of a Conjugate Acid or Base The Relationship Between Ka and Kb of a Conjugate Acid Base Pair 82
16. 7 Conjugate Acid Base Pairs The Strength of a Conjugate Acid or Base The chloride ion, which is the conjugate base of a strong acid, is an example of a weak conjugate base. 83
16. 7 Conjugate Acid Base Pairs The Strength of a Conjugate Acid or Base The fluoride ion, which is the conjugate base of a weak acid, is an example of a strong conjugate base. Conversely, a strong base has a weak conjugate acid and a weak base has a strong conjugate acid. 84
16. 7 Conjugate Acid Base Pairs The Strength of a Conjugate Acid or Base 85
16. 7 Conjugate Acid Base Pairs The Strength of a Conjugate Acid or Base 86
16. 7 Conjugate Acid Base Pairs The Strength of a Conjugate Acid or Base It is important to recognize that the words strong and weak do not mean the same thing in the context of conjugate acids and conjugate bases as they do in the context of acids and bases in general. A strong conjugate reacts with water—either accepting a proton from it or donating a proton to it—to a small but measurable extent. 87
16. 7 Conjugate Acid Base Pairs The Strength of a Conjugate Acid or Base A strong conjugate acid acts as a weak Brønsted acid in water; and a strong conjugate base acts as a weak Brønsted base in water. A weak conjugate does not react with water to any measurable extent. 88
16. 7 Conjugate Acid Base Pairs The Relationship Between Ka and Kb of a Conjugate Acid Base Pair 89
16. 7 Conjugate Acid Base Pairs The Relationship Between Ka and Kb of a Conjugate Acid Base Pair 90
16. 7 Conjugate Acid Base Pairs The Relationship Between Ka and Kb of a Conjugate Acid Base Pair 91
SAMPLE PROBLEM 16. 17 Determine (a) Kb of the acetate ion (CH 3 COO–), (b) Ka of the methylammonium ion (CH 3 NH 3+ ), (c) Kb of the fluoride ion (F–), and (d) Ka of the ammonium ion (NH 4+ ). Setup 92
SAMPLE PROBLEM 16. 17 Solution 93
16. 8 Diprotic and Polyprotic Acids Topics Diprotic and Polyprotic Acids 94
16. 8 Diprotic and Polyprotic Acids 95
16. 8 Diprotic and Polyprotic Acids 96
16. 8 Diprotic and Polyprotic Acids 97
SAMPLE PROBLEM 16. 18 Oxalic acid (H 2 C 2 O 4) is a poisonous substance used mainly as a bleaching agent. Calculate the concentrations of all species present at equilibrium in a 0. 10 M solution at 25°C. Setup 98
SAMPLE PROBLEM 16. 18 Setup Solution 99
SAMPLE PROBLEM 16. 18 Solution 100
SAMPLE PROBLEM 16. 18 Solution 101
SAMPLE PROBLEM 16. 18 Solution 102
SAMPLE PROBLEM 16. 18 Solution 103
16. 9 Molecular Structure and Acid Strength Topics Hydrohalic Acids Oxoacids Carboxylic Acids 104
16. 9 Molecular Structure and Acid Strength Hydrohalic Acids The strength of an acid is measured by its tendency to ionize: Two factors influence the extent to which the acid undergoes ionization. One is the strength of the H—X bond. The stronger the bond, the more difficult it is for the HX molecule to break up and hence the weaker the acid. The other factor is the polarity of the H—X bond. 105
16. 9 Molecular Structure and Acid Strength Hydrohalic Acids If the bond is highly polarized (i. e. , if there is a large accumulation of positive and negative charges on the H and X atoms, respectively), HX will tend to break up into H+ and X– ions. A high degree of polarity, therefore, gives rise to a stronger acid. 106
16. 9 Molecular Structure and Acid Strength Hydrohalic Acids 107
16. 9 Molecular Structure and Acid Strength Oxoacids An oxoacid contains hydrogen, oxygen, and a central, nonmetal atom. 108
16. 9 Molecular Structure and Acid Strength Oxoacids To compare their strengths, it is convenient to divide the oxoacids into two groups: 1. Oxoacids having different central atoms that are from the same group of the periodic table and that have the same oxidation number. 109
16. 9 Molecular Structure and Acid Strength Oxoacids Within this group, acid strength increases with increasing electronegativity of the central atom. Cl is more electronegative than Br; the O—H bond is more polar in chloric acid than in bromic acid. 110
16. 9 Molecular Structure and Acid Strength Oxoacids 2. Oxoacids having the same central atom but different numbers of oxygen atoms. Within this group, acid strength increases with increasing oxidation number of the central atom. 111
16. 9 Molecular Structure and Acid Strength Oxoacids The ability of chlorine to draw electrons away from the OH group (thus making the O—H bond more polar) increases with the number of electronegative O atoms attached to Cl. 112
SAMPLE PROBLEM 16. 19 Predict the relative strengths of the oxoacids in each of the following groups: (a) HCl. O, HBr. O, and HIO; (b) HNO 3 and HNO 2. Strategy In each group, compare the electronegativities or oxidation numbers of the central atoms to determine which O H bonds are the most polar. The more polar the O—H bond, the more readily it is broken and the stronger the acid. 113
SAMPLE PROBLEM 16. 19 Setup (a) In a group with different central atoms, we must compare electronegativities. The electronegativities of the central atoms in this group decrease as follows: Cl > Br > I. (b) These two acids have the same central atom but differ in the number of attached oxygen atoms. In a group such as this, the greater the number of attached oxygen atoms, the higher the oxidation number of the central atom and the stronger the acid. 114
SAMPLE PROBLEM 16. 19 Solution 115
16. 9 Molecular Structure and Acid Strength Carboxylic Acids The conjugate base of a carboxylic acid, called a carboxylate anion, RCOO–, can be represented by more than one resonance structure: 116
16. 9 Molecular Structure and Acid Strength Carboxylic Acids The strength of carboxylic acids depends on the nature of the R group. The presence of the electronegative Cl atom in chloroacetic acid shifts the electron density toward the R group, thereby making the O—H bond more polar. Chloroacetic acid is the stronger of the two acids. 117
16. 10 Acid Base Properties of Salt Solutions Topics Basic Salt Solutions Acidic Salt Solutions Neutral Salt Solutions Salts in Which Both the Cation and the Anion Hydrolyze 118
16. 10 Acid Base Properties of Salt Solutions Basic Salt Solutions Consider a solution of the salt sodium fluoride (Na. F). This is a specific example of salt hydrolysis, in which ions produced by the dissociation of a salt react with water to produce either hydroxide ions or hydronium ions—thus impacting p. H. 119
16. 10 Acid Base Properties of Salt Solutions Basic Salt Solutions In general, an anion that is the conjugate base of a weak acid reacts with water to produce hydroxide ion. Other examples include the acetate ion (CH 3 COO–), the nitrite ion (NO 2–), the sulfite ion (SO 32–), and the hydrogen carbonate ion (HCO 3–). 120
SAMPLE PROBLEM 16. 20 Calculate the p. H of a 0. 10 M solution of sodium fluoride (Na. F) at 25°C. Setup 121
SAMPLE PROBLEM 16. 20 Solution 122
16. 10 Acid Base Properties of Salt Solutions Acidic Salt Solutions 123
SAMPLE PROBLEM 16. 21 Calculate the p. H of a 0. 10 M solution of ammonium chloride (NH 4 Cl) at 25°C. Setup 124
SAMPLE PROBLEM 16. 21 Solution 125
16. 10 Acid Base Properties of Salt Solutions Acidic Salt Solutions The metal ion in a dissolved salt can also react with water to produce an acidic solution. The extent of hydrolysis is greatest for the small and highly charged metal cations such as Al 3+, Cr 3+, Fe 3+, Bi 3+, and Be 2+. 126
16. 10 Acid Base Properties of Salt Solutions Acidic Salt Solutions For example, when aluminum chloride dissolves in water, each Al 3+ ion becomes associated with six water molecules. 127
16. 10 Acid Base Properties of Salt Solutions Acidic Salt Solutions Al(OH)(H 2 O)52+ can undergo further ionization: and so on. It is generally sufficient, however, to take into account only the first stage of hydrolysis when determining the p. H of a solution that contains metal ions. 128
16. 10 Acid Base Properties of Salt Solutions Neutral Salt Solutions The extent of hydrolysis is greatest for the smallest and most highly charged metal ions because a compact, highly charged ion is more effective in polarizing the O—H bond and facilitating ionization. This is why relatively large ions of low charge, including the metal cations of Groups 1 A and 2 A (the cations of the strong bases), do not undergo significant hydrolysis (Be 2+ is an exception). Thus, most metal cations of Groups 1 A and 2 A do not impact the p. H of a solution. 129
16. 10 Acid Base Properties of Salt Solutions Neutral Salt Solutions Similarly, anions that are conjugate bases of strong acids do not hydrolyze to any significant degree. Consequently, a salt composed of the cation of a strong base and the anion of a strong acid, such as Na. Cl, produces a neutral solution. 130
16. 10 Acid Base Properties of Salt Solutions Neutral Salt Solutions 131
SAMPLE PROBLEM 16. 22 Predict whether a 0. 10 M solution of each of the following salts will be basic, acidic, or neutral: (a) Li. I, (b) NH 4 NO 3, (c) Sr(NO 3)2, (d) KNO 2, (e) Na. CN. Strategy Identify the ions present in each solution, and determine which, if any, will impact the p. H of the solution. 132
SAMPLE PROBLEM 16. 22 (a) Li. I, (b) NH 4 NO 3, (c) Sr(NO 3)2, (d) KNO 2, (e) Na. CN. Setup (a) Ions in solution: Li+ and I–. Li+ is a Group 1 A cation; I– is the conjugate base of the strong acid HI. Therefore, neither ion hydrolyzes to any significant degree. (b) Ions in solution: NH 4+ and NO 3–. NH 4+ is the conjugate acid of the weak base NH 3; NO 3– is the conjugate base of the strong acid HNO 3. In this case, the cation will hydrolyze, making the p. H acidic: 133
SAMPLE PROBLEM 16. 22 (a) Li. I, (b) NH 4 NO 3, (c) Sr(NO 3)2, (d) KNO 2, (e) Na. CN. Setup c. Ions in solution: Sr 2+ and NO 3–. Sr 2+ is a heavy Group 2 A cation; NO 3– is the conjugate base of the strong acid HNO 3. Neither ion hydrolyzes to any significant degree. d. Ions in solution: K+ and NO 2–. K+ is a Group 1 A cation; NO 2 – is the conjugate base of the weak acid HNO. In this case, 2 the anion hydrolyzes, thus making the p. H basic: 134
SAMPLE PROBLEM 16. 22 (a) Li. I, (b) NH 4 NO 3, (c) Sr(NO 3)2, (d) KNO 2, (e) Na. CN. Setup e. Ions in solution: Na+ and CN–. Na+ is a Group 1 A cation; CN – is the conjugate base of the weak acid HCN. In this case, too, the anion hydrolyzes, thus making the p. H basic: 135
SAMPLE PROBLEM 16. 22 (a) Li. I, (b) NH 4 NO 3, (c) Sr(NO 3)2, (d) KNO 2, (e) Na. CN. Solution 136
16. 10 Acid Base Properties of Salt Solutions Salts in Which Both the Cation and the Anion Hydrolyze • When Kb > Ka, the solution is basic. • When Kb < Ka, the solution is acidic. • When Kb Ka, the solution is neutral or nearly neutral. 137
16. 11 Acid Base Properties of Oxides and Hydroxides Topics Oxides of Metals and Nonmetals Basic and Amphoteric Hydroxides 138
16. 11 Acid Base Properties of Oxides and Hydroxides Oxides of Metals and Nonmetals 139
16. 11 Acid Base Properties of Oxides and Hydroxides Oxides of Metals and Nonmetals 140
16. 11 Acid Base Properties of Oxides and Hydroxides Oxides of Metals and Nonmetals Aluminum oxide (Al 2 O 3) is amphoteric. 141
16. 11 Acid Base Properties of Oxides and Hydroxides Oxides of Metals and Nonmetals Some transition metal oxides in which the metal has a high oxidation number act as acidic oxides. 142
16. 11 Acid Base Properties of Oxides and Hydroxides Basic and Amphoteric Hydroxides All the alkali and alkaline earth metal hydroxides, except Be(OH)2, are basic. Be(OH)2, Al(OH)3, Sn(OH)2, Pb(OH)2, Cr(OH)3, Cu(OH)2, Zn(OH)2, and Cd(OH)2 are amphoteric. All amphoteric hydroxides are insoluble, but beryllium hydroxide reacts with both acids and bases as follows: 143
16. 11 Acid Base Properties of Oxides and Hydroxides Basic and Amphoteric Hydroxides Aluminum hydroxide reacts with both acids and bases in a similar fashion: 144
16. 12 Lewis Acids and Bases Topics Lewis Acids and Bases 145
16. 12 Lewis Acids and Bases A Lewis base is a substance that can donate a pair of electrons. A Lewis acid is a substance that can accept a pair of electrons. 146
16. 12 Lewis Acids and Bases 147
16. 12 Lewis Acids and Bases 148
SAMPLE PROBLEM 16. 23 Identify the Lewis acid and Lewis base in each of the following reactions: Setup (a) (b) Metal ions act as Lewis acids, accepting electron pairs from anions or molecules with lone pairs. 149
SAMPLE PROBLEM 16. 23 Solution (a) (b) Hg 2+ accepts four pairs of electrons from the CN– ions. Therefore, Hg 2+ is the Lewis acid and CN– is the Lewis base. 150
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