Chapter 10 Review, pages 492–497
Knowledge
1. (d)
2. (c)
3. (b)
4. (b)
5. (d)
6. (c)
7. (b)
8. (a)
9. (a)
10. False. Acids react with carbonates to produce carbon dioxide gas.
11. False. The correct name of HClO2(aq) is chlorous acid.
12. True
13. False. In a weak acid, only a small percentage of molecules ionize in solution.
14. True
15. False. Acidic solutions contain many hydrogen ions.
16. True
17. False. The endpoint of a titration depends on the choice of indicator.
18. True
19. (a) (i)
(b) (iii)
(c) (v)
(d) (iv)
(e) (ii)
20. The metal was more reactive than hydrogen because it replaced hydrogen in the acid.
21. An oxyacid contains oxygen, as well as hydrogen and at least one other element. A hydroacid does not contain oxygen.
22. The word “acid” comes from the Latin word acidus, which means sour. A property of acids
is that they taste sour.
23. The process of saponification is used to produce soaps using a fat and a base.
24. (a) When calcium carbonate is dropped into an acid, carbon dioxide gas is produced.
(b) When magnesium is dropped into an acid, hydrogen gas is produced.
25. A base feels slippery because the base reacts with the oils on the skin to produce a soap-like
substance.
26. When calcium chloride dissolves in water, the water molecules surround the ions, pulling
them away from the crystals and into solution. This process is called dissociation.
27. A strong acid, such as hydrochloric acid, completely ionizes in solution to form hydrogen
ions and chloride ions. A weak acid only partially ionizes in solution.
28. The process of ion formation in an acid is ionization. During ionization, a dissolved
molecular compound reacts with water to produce ions. The process of ion formation in a base is
dissociation. During dissociation, ions already in existence in an ionic compound separate as the
compound dissolves.
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Chapter 10: Acids and Bases
10-2
29. To determine which solution is the strong acid and which is the weak acid, you could
carefully place a nail into each solution. The strong acid reacts with the iron faster than the weak
acid does. The most obvious evidence is that the nail and the strong acid produce bubbles of
hydrogen more rapidly.
30. The strength of an electrolyte depends on the concentration of ions in solution. A weak base
is a relatively poor conductor because it has a relatively low concentration of ions in solution.
31. Tartaric acid must be a weak acid because it is safe to eat. Strong acids can damage human
tissue.
32. Using several trials for a titration reduces the chance of error and improves the reliability of
the data.
33. It is necessary to write a balanced chemical equation before any calculations are done so that
mole ratios of the acid and base can be determined. These mole ratios are used in the
calculations.
34. The equivalence point for a titration is the actual point at which the neutralization is
complete. At the equivalence point, equal amounts of the two reactants have been combined. The
endpoint is where an observable change occurs, such as the change in colour of an indicator. For
the results of the titration to be accurate, the endpoint should be as close as possible to the
equivalence point.
35. The purpose of titrating a solution against a primary standard is to allow an accurate
determination of the concentration of an unknown solution to be made. A primary standard is
pure and chemically stable. Since its concentration and volume do not change with conditions, an
accurate determination of the concentration of an unknown solution can be made when it is
titrated against a primary standard.
36. Before the titration, find the volume of solution in the burette by reading the level at the
bottom of the meniscus. After the titration, read the level of the solution again. To determine
how much solution was used during the titration, subtract the initial volume reading from the
final reading.
37. Answers may vary. Sample answer: It is necessary to rinse the burette with distilled water to
remove impurities in the burette. It is necessary to rinse the burette with the titrant to remove any
distilled water present so the solution in the burette will not be diluted.
Understanding
38. (a) The term “alkali” refers to a base. It comes from the Arabic term for “basic.”
(b) The names of the alkali metals (Group 1 elements) and the alkaline earth metals (Group 2
elements) both come from the term “alkali.”
(c) The alkali metals and the alkaline earth metals form basic oxides.
39. (a) Step 1. Oxygen is not present.
Step 2. The acid with the formula HBr(aq) is hydrobromic acid.
(b) Step 1. Oxygen is present. It is an oxyacid
Step 2. The oxyanion is PO33–, phosphite ion.
Step 3. The acid with the formula H3PO3(aq) is phosphorous acid.
(c) Step 1. Oxygen is present. It is an oxyacid
Step 2. The oxyanion is NO3–, nitrate ion.
Step 3. The acid with the formula HNO3(aq) is nitric acid.
(d) Step 1. Oxygen is present. It is an oxyacid
Step 2. The oxyanion is perchlorate ion, ClO4–.
Step 3. The acid with the formula HClO4(aq) is perchloric acid.
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Chapter 10: Acids and Bases
10-3
40. (a) Ba(OH)2(aq) is barium hydroxide.
(b) Li(OH)(aq) is lithium hydroxide.
(c) Sr(OH)2(aq) is strontium hydroxide.
(d) Be(OH)2(aq) is beryllium hydroxide.
41. (a) Step 1. Since the name does not contain the prefix hydro-, it is an oxyacid.
Step 2. The acid contains the phosphate ion, PO43–.
Step 3. Using the zero-sum rule, three H+ ions are required to produce a neutral acid molecule.
Step 4. The formula of phosphoric acid is H3PO4(aq).
(b) Step 1. Since the name does not contain the prefix hydro-, it is an oxyacid.
Step 2. The acid contains the nitrite ion, NO2–.
Step 3. The formula of nitrous acid is HNO2(aq).
(c) Step 1. Since the name contains the prefix hydro-, oxygen is present.
Step 2. The acid contains the sulfide ion, S2–.
Step 3. Using the zero-sum rule, two H+ ions are required to produce a neutral acid molecule.
Step 4. The formula of hydrosulfuric acid is H2S(aq).
(d) Step 1. Since the name contains the prefix hydro-, oxygen is present.
Step 2. The acid contains the telluride ion, Te2–.
Step 3. Using the zero-sum rule, two H+ ions are required to produce a neutral acid molecule.
Step 4. The formula of hydrotelluric acid is H2Te(aq).
42. (a) The chemical formula for calcium hydroxide is Ca(OH)2(aq).
(b) The chemical formula for ammonium hydroxide is NH4OH(aq).
(c) The chemical formula for sodium hydroxide is NaOH(aq).
(d) The chemical formula for aluminum hydroxide is Al(OH)3(aq).
43. (a) NR. Silver is not reactive with hydrochloric acid.
(b) Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)
(c) 2 K(s) + 2 HCl(aq) → 2 KCl(aq) + H2(g)
(d) NR. Silver is not reactive with hydrochloric acid.
(e) Ca(s) + 2 HCl(aq) → CaCl2(aq) + H2(g)
(f) 2 Al(s) + 6 HCl(aq) → 2 AlCl3(aq) + 3 H2(g)
44. In the general formula of an acid, the "H" represents hydrogen, the "A" represents the
remaining part of the chemical formula, and "(aq)" indicates that the compound is dissolved in
water. The general formula HA(aq) is effective because, according to the Arrhenius definition, all
acids contain hydrogen. They also contain a part that will produce an anion, A, in solution. The (aq)
is necessary because acids only show their properties when they are in aqueous solutions.
45. The formula for carbonic acid is H2CO3(aq) and the formula for phosphoric acid is H3PO4(aq).
46. (a) The three compounds are most likely weak bases since they react with acids.
(b) NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
Mg(OH)2(s) + 2 HCl(aq) → 2 MgCl2(aq) + 2 H2O(l)
CaCO3(s) + 2 HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
47. (a) Since battery acid has a pH of 0 and tomatoes have a pH of 4, battery acid is 104 times
more acidic than tomatoes.
(b) Since milk of magnesia has a pH of 10 and tomatoes have a pH of 4, milk of magnesia is 106
times more basic than tomatoes.
48. The dilution of seawater with pure water will bring the pH closer to 7, which is the pH of
pure water.
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Chapter 10: Acids and Bases
10-4
49. (a) The volume of titrant in each trial is calculated as follows:
Trial 1: 36.87 mL – 12.24 mL = 24.63 mL
Trial 2: 36.06 mL – 11.46 mL = 24.60 mL
Trial 3: 35.51 mL – 10.59 mL = 24.92 mL
The volume of titrant used in each trial is 24.63 mL, 24.60 mL, and 24.92 mL.
(b) Given: three volumes of titrant–24.63 mL, 24.60 mL, 24.92 mL
Required: average volume of acid used, Vtitrant
Solution:
Calculate the average volume of titrant.
24.63 mL + 24.60 mL + 24.92 mL
Vtitrant(average) =
3
Vtitrant(average) = 24.72 mL
Statement: The average volume of titrant used was 24.72 mL.
50. Given: concentration of base, cNaOH = 0.10 mol/L
volume of acid, VHCl = 20.00 mL
volume of base, VNaOH(average) = 18.54 mL
Required: amount concentration of acid, cHCl
Analysis: c =
n
V
Solution:
Step 1. Convert the volume of solutions to litres.
1L
VHCl = 20.00 mL !
1000 mL
VHCl = 2.000 ! 10 "2 L
VNaOH = 18.54 mL !
1L
1000 mL
VNaOH = 1.854 ! 10 "2 L
Step 2. Write a balanced equation for the reaction showing the listed values.
HCl(aq)
+
NaOH(aq)
→
NaCl(aq)
+
H2O(l)
–2
–2
2.000 × 10 L
1.854 × 10 L
cHCl
0.10 mol/L
Step 3. Use the concentration equation to determine the amount of base.
nNaOH = cNaOHVNaOH
=
0.10 mol
! 1.854 ! 10 "2 L
1L
nNaOH = 1.854 ! 10 "3 mol
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Chapter 10: Acids and Bases
10-5
Step 4. Use the amount of base and mole ratio in a balanced equation to determine the amount of
acid.
1 mol HCl
nHCl = 1.854 ! 10 "3 mol NaOH !
1 mol NaOH
nHCl = 1.854 ! 10 "3 mol HCl
Step 5. Use the concentration equation to determine the concentration of acid.
n
cHCl = HCl
VHCl
=
1.854 ! 10 "3 mol
2.000 ! 10 "2 L
mol
cHCl = 0.93
L
Statement: The amount concentration of the hydrochloric acid is 0.93 mol/L.
51. (a) Table 2 Titration Data
Trial
1
2
3
final burette volume 24.83
16.35
28.95
reading (mL)
initial burette
8.54
0.03
12.64
volume reading
(mL)
volume of base
16.29
16.32
16.31
added (mL)
(b) Given: three volumes of base–16.20 mL, 16.32 mL, 16.31 mL
Required: average volume of base used, VKOH
Solution:
Calculate the average volume of base used.
16.29 mL + 16.32 mL + 16.31 mL
VKOH(average) =
3
VKOH(average) = 16.31 mL
Statement: The average volume of base used is 16.31 mL.
(c) H2SO4(aq) + 2 KOH(aq) → K2SO4(aq) + 2 H2O(l)
(d) Given: concentration of base, cKOH = 0.10 mol/L
volume of acid, VH SO = 15.0 mL
2
4
average volume of base, VKOH(average) = 16.31 mL
Required: amount concentration of acid, cH SO
2
4
n
Analysis: c =
V
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Chapter 10: Acids and Bases
10-6
Solution:
Step 1. Convert the volume of solution to litres.
1L
VH SO = 15.0 mL !
2
4
1000 mL
VH SO = 0.015 L
2
4
VKOH(average) = 16.31 mL !
1L
1000 mL
VKOH(average) = 0.016 31 L
Step 2. Write a balanced equation for the reaction.
H2SO4(aq)
+ 2 KOH(aq) → K2SO4(aq) + 2 H2O(l)
0.015 L
0.016 31 L
0.10 mol/L
cH SO
2
4
Step 3. Use the concentration equation to determine the amount of base.
nKOH = cKOHVKOH(average)
0.10 mol
! 0.01631 L
1L
nKOH = 0.001631 mol
Step 4. Use the amount of base and mole ratio in the balanced equation to determine the amount
of acid.
1 mol H SO
2
4
nH SO = 0.001 631 mol KOH !
2
4
2 mol KOH
=
nH SO = 8.155 ! 10 "4 mol H SO
2
4
2
4
Step 5. Use the concentration equation to determine the concentration of acid.
nH SO
cH SO = 2 4
2
4
VH SO
2
4
8.155 ! 10 "4 mol
=
0.015 L
mol
cH SO = 0.054
2
4
L
Statement: The amount concentration of the sulfuric acid is 0.054 mol/L.
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Chapter 10: Acids and Bases
10-7
52. (a) 26.23 mL – 0.21 mL = 26.02 mL
The volume of primary standard solution used in this trial was 26.02 mL.
(b) Given: mass of sodium carbonate, mNa CO = 0.53 g
2
3
molar mass of sodium carbonate = 105.99 g/mol
volume of standard solution, VNa CO (standard) = 100 mL
2
3
volume of titrated solution, VNa CO = 26.02 mL
2
3
Required: amount of sodium carbonate in titrated solution, nNaCO
3
Solution:
Step 1. Convert the volume of solutions used to litres.
1L
VNa CO (standard) = 100 mL !
2
3
1000 mL
VNa CO (standard) = 0.100 L
2
3
VNa CO = 26.02 mL !
2
3
1L
1000 mL
VNa CO = 0.026 02 L
2
3
Step 2. Convert mass of sodium carbonate to amount in 100 mL of solution.
1 mol
nNa CO = 0.53 g !
2
3
105.99 g
nNa CO = 5.00 ! 10 "3 mol
2
3
Step 3. Use the concentration equation to determine the concentration of sodium carbonate in the
standard solution.
nNa CO
2
3
cNa CO =
2
3
VNa CO (standard)
2
3
5.00 ! 10 "3 mol
0.100 L
mol
cNa CO = 5.00 ! 10 "2
2
3
L
Step 4. Use the concentration equation to determine the amount of sodium carbonate in the
titrated solution.
nNa CO = cNa CO VNa CO
=
2
3
2
=
3
2
3
"2
5.00 ! 10 mol
! 0.02602 L
1L
nNa CO = 1.3 ! 10 "3 mol
2
3
Statement: The amount of sodium carbonate that reacted with the acid is 1.3 × 10–3 mol.
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Chapter 10: Acids and Bases
10-8
(c) Given: amount of sodium carbonate that reacted with the acid, nNa CO = 1.3 ! 10 –3 mol
2
3
volume of acid, VHCl = 18 mL
Required: amount concentration of hydrochloric acid, cHCl
Analysis: c =
n
V
Solution:
Step 1. Convert the volume of solution used to litres.
1L
VHCl = 18 mL !
1000 mL
VHCl = 0.018 L
Step 2. Write the balanced equation and list the given values.
Na2CO3(aq)
+ 2 HCl(aq)
→ 2 NaCl(aq) + H2O(l) + CO2(g)
–3
1.3 × 10 mol
0.018 L
cHNO
3
Step 3. Use the amount and the mole ratio in the balanced equation to determine the amount of
the acid.
2 mol HCl
nHCl = 1.3 ! 10 "3 mol Na CO !
2
3
1 mol Na CO
2
3
"3
nHCl = 2.6 ! 10 mol HCl
Step 4. Use the concentration equation to determine the concentration of acid.
n
cHCl = HCl
VHCl
2.6 ! 10 "3 mol
=
0.018 L
mol
cHCl = 0.14
L
Statement: The amount concentration of hydrochloric acid is 0.14 mol/L.
Analysis and Application
53. (a) The type of compound you would expect to be present in an alkaline battery is a base.
(b) The specific compound these batteries contain is potassium hydroxide, KOH.
(c) The purpose of an alkaline battery is to provide electric current. This purpose reveals that the
alkaline compound must be a good conductor of electricity.
54. The cleaner that contains vinegar would be a better choice to remove hard water deposits
than the cleaner that contains ammonium hydroxide. Vinegar is acidic, and acids react with
carbonates. This reaction would break down the compound, removing the deposit. Bases, such as
ammonium hydroxide, do not react with carbonates.
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Chapter 10: Acids and Bases
10-9
55. (a) 2 NO2(g) + H2O(l) → HNO2(aq) + HNO3(aq)
The products are nitrous acid, HNO2(aq), and nitric acid, HNO3(aq)
(b) SO2(g) + H2O(l) → H2SO3(aq)
The product is sulfurous acid.
(c) SO3(g) + H2O(l) → H2SO4(aq)
The product is sulfuric acid.
56. Nitrous acid is not the correct name for this acid. Its correct name is nitric acid. The first
acid’s name is correct because SO32– is the sulfite ion. Acids formed from an -ite ion are named
with an -ous suffix. Even though it has the same number of oxygen atoms as the sulfite ion, NO3–
is the nitrate ion. Acids formed from an -ate ion are named with an -ic suffix, such as nitric acid.
57. Nitric acid might be used to make ammonium nitrate. In a neutralization reaction between
nitric acid and ammonium hydroxide, water and ammonium nitrate are produced.
HNO3(aq) + NH4OH(aq) → NH4NO3(aq) + H2O(l)
58. (a) The ions produced when water ionizes are hydrogen ions, H+(aq), and hydroxide ions,
OH‒(aq).
(b) These ions are likely to occur in equal concentrations in pure water. Their ratio will be 1:1.
59. (a) Answers may vary. Sample answer: The student could check the electrical conductivity of
the liquids. Water would not conduct electricity at all; the weak acid and the weak base would
conduct some; and the strong acid and the strong base would conduct electricity well. The
student could then use an acid‒base indicator to distinguish between the strong acid and the
strong base, and between the weak acid and the weak base. Alternatively, the student could use a
pH meter to measure the pH of each liquid. The solution with the lowest pH is a strong acid. The
solution with the next lowest pH is the weak acid. The liquid at pH 7 is pure water. The weak
base will have a pH slightly above 7, and the strong base will have the highest pH.
(b) The student needs to know that the acids and bases have equal concentrations so that he can
distinguish between the strong and weak acids and bases. It is possible that a concentrated weak
acid could have a lower pH than a very dilute strong acid. Similarly, a concentrated weak base
could possibly have a higher pH than a very dilute strong base.
60. Answers may vary. Sample answer: When hydrochloric acid reacts with sodium hydroxide
solution, the products (sodium chloride and water) are neutral. At the equivalence point, the pH
should be 7. You therefore need to select an acid‒base indicator that changes colour at a pH of 7.
Phenolphthalein and methyl orange do not change colour at the equivalence point, so they would
not give accurate results
Evaluation
61. (a) Since the solution is blue and Table 1 shows bromothymol blue and litmus are blue in a
base, the solution is most likely basic.
(b) To determine which indicator was used, an acid could be added until a colour change occurs.
If the solution turns red, the indicator is litmus. If the solution turns green and then yellow, the
indicator is bromothymol blue.
62. (a) To properly dispose of a nitric acid solution with a pH of 4, a base should be added until
the pH is approximately 7. A possible test is adding a drop of phenolphthalein indicator solution
to the acid. When it changes from colourless to very slightly pink, the solution is neutral.
(b) To properly dispose of a sodium hydroxide solution with a pH of 10, add an acid until the pH
is approximately 7. A possible test is adding a drop of litmus solution to the base. When it starts
to change from blue to red, the solution is neutral.
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Chapter 10: Acids and Bases
10-10
63. (a) Answers may vary. Sample answer: The equation VA cA = VBcB could be used in a titration
between hydrochloric acid and sodium hydroxide because the concentrations are in a 1 : 1 ratio.
(b) Answers may vary. Sample answer: The equation VA cA = VBcB could not be used in a titration
between sulfuric acid and sodium hydroxide because the concentrations are not in a 1 : 1 ratio.
The concentrations of these reactants are in a 2:1 ratio.
64. Since the sodium hydroxide had been stored in humid conditions, the mass of the sodium
hydroxide would include the mass of some water. If the measured mass was used to determine
the concentration of the sodium hydroxide solution, the calculated concentration would have
been higher than the actual concentration. Since the concentration of the acid is proportional to
the concentration of the base, the calculated concentration of the acid would have also been
higher than the actual concentration.
65. Answers may vary. Sample answer: The student who said that the titrant level can be below
the 0 mL mark is correct. The initial volume reading can be below the 0 mL mark as long as it is
read and recorded accurately, and as long as there is enough titrant in the burette to perform the
titration. The total volume of titrant used can be determined by subtracting the initial volume
reading from the final volume reading.
66. (a) Since Thomas used a graduated cylinder, his volume measurements were not as precise as
they should be. Thomas should use a burette in good working order, instead of a graduated
cylinder, to obtain better results.
(b) Latoya added the titrant only until the indicator first changed colour, which indicates only
that the endpoint has been reached at the location where the titrant was added. To measure the
titrant used to reach the equivalence point, Latoya should swirl the solution, adding titrant drop
by drop until the endpoint indicates the equivalence point of the entire sample.
Reflect on Your Learning
67. (a) Answers may vary. Sample answer: I drank citric acid in orange juice and sprinkled
acetic acid (vinegar) on my fries. I rode in a car that had acid in its battery.
(b) Answers may vary. Sample answer: Bases were in some of the cleaners that I used, including
soap.
(c) Answers may vary. Sample answer: I knew that the materials were acids because the orange
juice and the vinegar tasted sour. I knew that the materials were basic because the cleaner felt
slippery. I also knew that the battery acid reacted with the lead metal in the battery to start the
car.
68. (a) Answers may vary. Sample answer: Sample answer: I thought all acids were dangerous
and would harm my skin if I touched them.
(b) Answers may vary. Sample answer: I learned that some acids are weak, such as the acids in
foods, and that they are not harmful. I learned that diluting even strong acids makes them
relatively safe to handle. However, I learned to be cautious when handling all acids and bases
because many of them are irritating or corrosive, and could harm my skin if they are touched.
69. Citric acid is most likely a weak acid because it is safe to touch and to eat, and will not damage
human tissue. If it were a strong acid, we could not eat fruits that contain citric acid.
70. Answers may vary. Sample answer: Ethanoic acid is a weak acid, which should not harm the
environment if it is applied directly to the plant. Strong acids, such as sulfuric acid, could
damage other organisms in the environment, pollute the soil, and possibly even damage concrete
and other surfaces. In addition, sulfuric acid poses a health hazard to the person applying it to the
weeds.
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Chapter 10: Acids and Bases
10-11
71. (a) The stopcock on the burette is closed when the handle is perpendicular to the burette tube.
It is open when the handle is parallel to the burette tube.
(b) Answers may vary. Sample answer: Shutoff valves in pipes are positioned the same as with
the stopcock. The valve is closed when the handle is perpendicular to the pipe and open when the
handle is parallel to the pipe.
(c) Answers may vary. Sample answer: I have noticed similar shutoff valves in gas pipes and in
controllers for garden hoses.
Research
72. (a) A binary acid contains hydrogen and one other non-metallic element.
(b) Answers may vary. Sample answer: An example of an acid that is neither an oxyacid nor a
binary acid is hydrocyanic acid, HCN.
(c) Answers may vary. Sample answer: Hydrocyanic acid is an extremely poisonous gas. It is
used as a fumigating agent, in hardening iron and steel, and in concentrating ores, such as gold
ore.
73. (a) (i) Methyl red is red in an acidic solution and yellow in a base.
(ii) Bromophenol blue is yellow in an acid and blue in a base.
(iii) Bromcresol purple changes from yellow to purple as the solution changes from acid to base.
(b) A universal indicator is a mixture of several different indicators, each of which changes
colour at a different pH. For example, it not only shows that a solution is acidic, but it also shows
how acidic it is. In a very acidic solution, it is red. In a moderately acidic solution, it is
orange/yellow. A neutral solution is green. The colour of a moderately basic solution is blue and
if the solution is very basic, it is purple.
(c) Answers may vary. Sample answer: Natural indicators include red cabbage, blackberries,
raspberries, and red onion. Red cabbage juice acts as a universal indicator in that it changes
colour several times over a range of pH values. Blackberries and black raspberries change from
red in an acid to blue or purple in a base. Red onion is pale red in an acidic solution and green in
a basic solution.
74. (a) Factors that made the lake more acidic included acid rain formed from industrial air
pollutants and untreated effluent from industry that was poured into the lake.
(b) Factors that made the lake more basic included an increase in phosphorus loading. The main
source is general sewage effluent and especially sewage that includes large amounts of
phosphorus-containing detergents used in homes.
(c) Since the lake was basic, the factor that most affected the water was the phosphorus effluent,
which was more influential than factors that added acid to the lake.
(d) An agreement between Canada and the United States prohibited the use of certain detergents
containing phosphorus and required treatment of effluent before it was discharged into the lake.
These measures returned Lake Ontario to a pH that was more healthful for the organisms.
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Chapter 10: Acids and Bases
10-12
75. (a) According to the Brønsted‒Lowry theory, an acid is a proton (hydrogen ion) donor and a
base is a proton (hydrogen ion) acceptor.
(b) The Brønsted‒Lowry theory adds to the Arrhenius theory. When an acid produces a
hydrogen ion, it also donates that ion (proton) to a base. The hydroxide ion produced by an
Arrhenius base accepts a hydrogen ion (proton) from an acid, forming water.
(c) According to the Lewis theory, an acid is an electron pair acceptor and a base is an electron
pair donor.
(d) Ammonia is an Arrhenius base only if it is in water and forms ammonium hydroxide,
NH4OH(aq). Ammonia is a Brønsted‒Lowry base because it will accept a proton and become an
ammonium ion, NH4+. Ammonia is a Lewis base because the nitrogen atom in ammonia has an
unshared pair of electrons that it can donate during a chemical reaction.
76. (a) When a strong acid and a weak base react, the resulting solution is slightly acidic.
The pH of the solution at the equivalence point will be less than 7.
(b) Answers may vary. Sample answer: Indicators that would be appropriate for a titration
between a strong acid and a weak base would include methyl red, methyl orange, and
bromphenol blue. These indicators all change colour in a range of slightly to moderately acidic
pH values.
(c) When a weak acid and a strong base react, the resulting solution is slightly basic. The pH of
the solution at the equivalence point will be greater than 7.
(d) Answers may vary. Sample answer: Indicators that would be appropriate for a titration
between a strong acid and a weak base would include phenolphthalein, thymolphthalein, and
alizarin yellow. These indicators all change colour in a range of slightly to moderately basic pH
values.
77. (a) In addition to being pure and chemically stable, a primary standard should not form
hydrates and should have a relatively high molar mass. It should also be a solid that dissolves
readily.
(b) Answers may vary. Sample answer: In addition to KHP, potassium hydrogen iodate,
KH(IO3)2, is a primary standard used to titrate bases.
(c) Answers may vary. Sample answer: Two primary standards used to titrate acids are sodium
carbonate, Na2CO3, and tris-(hydroxymethyl)aminomethane (known as TRIS or THAM),
(CH2OH)3CNH2.
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Chapter 10: Acids and Bases
10-13