AP Chem Mr. Dehne
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AP Chem
Acids/Bases Worksheet Packet
WS#1: Nature of Acids/Bases
1. Write balanced equations that describe the following reactions.
a. the dissociation of perchloric acid in water
c. the dissociation of ammonium ion in water
b. the dissociation of propanoic acid
(CH2CH2CO2H) in water
2. For each of the following aqueous reactions, identify the acid, the base, the conjugate base, and the conjugate acid.
a. HF + H2 ↔ F- + H3O+
c. HSO4- + H2O ↔ SO42- + H3O+
b. H2SO4 + H2O ↔ H3O+ + HSO43. Classify each of the following as a strong acid (SA) or weak acid (WA).
a. HClO4 (aq)
c. H2SO4 (aq)
b. HOCl (aq)
d. H2SO3 (aq)
4. Use table in notes to order the following from the strongest to the weakest acid. H2O, HNO3, HOCl, NH4+
5. Use table in notes to order the following from the strongest to the weakest base. H 2O, NO3-, OCl-, NH3
6. You may need the table in your notes to answer the following questions.
a. Which is the stronger acid, HCl or H2O?
d. Which is the stronger base, Cl- or H2O?
b. Which is the stronger acid, H2O or HNO2?
e. Which is the stronger base, H2O or NO2-?
c. Which is the stronger acid, HCN or
f. Which is the stronger base, CN- or OC6H5?
HOC6H5?
WS#2: Autoionization of Water and the pH Scale
7. Calculate the [OH-] or [H+] of each of the following solutions at 25 oC. Identify each solution as neutral, acidic, or basic.
a. [H+] = 1.0x10-7M
e. [H+] = 1.9x10-11M
+
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b. [H ] = 6.7x10 M
f. [H+] = 2.3M
c. [OH ] = 3.6M
g. [OH-] = 2.2x10-3M
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d. [OH ] = 9.7x10 M
h. [OH-] = 1.0x10-7M
8. Values of K as a function of temperature are as follows:
Temperature (oC)
Kw
0
1.14x10-15
25
1.00x10-14
35
2.09x10-14
40
2.92x10-14
50
5.47x10-14
a. Is the autoionization of water exothermic or endothermic? b. Calculate [H+] and [OH-] in a neutral solution at 50oC.
9. Calculate the pH and pOH of the solutions in exercise 7.
10. The pOH of a sample of baking soda dissolved in water is 5.74 at 25 oC. Calculate the pH, [H+], and [OH-] for this sample. Is
the solution acidic or basic?
WS#3: Solutions of Acids
11. What are the major species present in 0.250M solutions of each of the following acids? Calculate the pH of each of these
solutions.
a. HClO4
b. HNO3
12. A solution is prepared by adding 50.0mL of 0.050M HCl to 150.0mL of 0.10M HNO3. Calculate the concentration of all
species in this solution.
13. Calculate the concentration of an aqueous HCl solution that has a pH = 2.50.
14. What are the major species present in 0.250M solutions of each of the following acids? Calculate the pH of each of these
solutions.
a. HNO2
b. CH3CO2H (HC2HO2)
15. A solution with a total volume of 250.0mL is prepared by diluting 20.0mL of glacial acetic acid with water. Calculate [H +]
and the pH of this solution. Assume that glacial acetic acid is pure liquid acetic acid with a density of 1.05g/cm3.
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16. Calculate the concentrations of all species present and the pH of a 0.020M HF solution.
17. Monochloracetic aci, HC2H2ClO2, is a skin irritant that is used in “chemical peels” intended to remove the top layer of dead
skin from the face and ultimately improve the complexion. The value of Ka is 1.35x10-3. Calculate the pH of a 0.10M
solution.
18. Calculate the pH of each of the following.
a. A solution containing 0.10M HCl and 0.10M HOCl b. A solution containing 0.050M HNO3 and 0.50M HC2H3O2.
19. Calculate the percent dissociation of the acid in each of the following solutions.
a. 0.50M acetic acid
b. 0.050M acetic acid
c. 0.0050M acetic acid
d. Use Le Chatelier’s principle to explain why percent dissociation increase as the concentration of a weak acid
decreases.
e. Even though the percent dissociation increases from solutions 1 to c, the [H +] decreases. Explain.
20. A 0.15M solution of a weak acid is 3.0% dissociated. Calculate Ka.
21. The pH of a 1.00x10-2M solution of cyanic acid (HOCN) is 2.77 at 25oC. Calculate Ka for HOCN from this result.
22. A solution of formic acid (HCOOH), Ka = 1.8x10-4) has a pH of 2.70. Calculate the initial concentration of formic acid in this
solution.
WS#3: Solutions of Bases
23. Write the reaction and corresponding Kb equilibrium expression for each of the following substances acting as bases.
a. NH3
b. C5H5N
24. Order the following bases from strongest to weakest. (Kb(NH3) = 1.8x10-5, Kb(C5H5N) = 1.7x10-9)
NO3-, H2O, NH3, C5H5N
25. Which is the stronger base (Kb(NH3) = 1.8x10-5, Kb(CH3NH2) = 4.38x10-4, Kb(NH3) = 1.8x10-5 )?
a. NO3- or NH3
b. H2O or NH3
c. OH- or NH3
d. NH3 or CH3NH2
26. Calculate the pH of the following solutions.
a. 0.10M NaOH
b. 1.0x10-10M NaOH
c. 2.0M NaOH
27. What are the major species present in 0.015M solution of each of the following bases?
a. KOH
b. Ba(OH)2
28. Calculate the concentration of an aqueous KOH solution that has a pH = 10.50.
29. What are the major species present in a 0.150M NH3 solution? Calculate the [OH-] and the pH of this solution.
30. Calculate [OH-], [H+], and the pH of 0.20M solution of each of the following amines.
a. triethylamine [(C2H5)3N, Kb = 4.0x10-4]
b. hydroxylamine (HONH2, Kb = 1.1x10-8)
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31. Calculate the pH of a 0.20M C2H5NH2 solution (Kb = 5.6x10 )
32. Calculate the percent ionization in each of the following solutions.
a. 0.10M NH3
b. 0.010M NH3
33. Codeine (C18H21NO3) is a derivative of morphine that is used as an analgesic, narcotic, or antitussive. It was once commonly
used in cough syrups but is now available only by prescription because of its addictive properties. If the pH of a 1.7x10-3M
solution of codeine is 9.59, calculate Kb.
WS#4: Polyprotic Acids/Acid-Base Properties of Salts/Relationships between Structure/Strengths of Acids-Bases/Lewis Acids-Bases
34. Write out the stepwise Ka reactions for the diprotic acid H2SO3.
35. Using the first dissociation step, calculate the pH of 0.10M solution of each of the following polyprotic acids.
a. H3PO4 (Ka = 7.5x10-3)
b. H2CO3 (Ka = 4.3x10-7)
36. Calculate the pH of a 2.0M H2SO4 solution.
37. Arrange the following 0.10M solutions in order of most acidic to most basic:
KOH, KCl, KCN, NH4Cl, HCl
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38. Given the Ka value for acetic acid is 1.8x10 and the Ka value for hypochlorous acidis 3.5x10-8, which is the stronger base,
OCl- or C2H3O2-?
39. Sodium azide (NaN3) is sometimes added to water to kill bacteria. Calculate the concentration of all species in a 0.010M
solution of NaN3. The Ka value for hydrazoic acid (HN3) is 1.9x10-5.
40. Calculate the pH of each of the following solutions. a. 0.10M CH3NH3Cl
b. 0.050M NaCN
41. An unknown salt is either NaCN, NaC2H3O2, NaF, NaCl, or NaOCl. When 0.100mol of the salt is dissolved in 1.00L of
water, the pH of the solution is 8.07. What is the identity of the salt?
42. Calculate the pH of a 0.050M Al(NO3)3 solution. The Ka value for Al(H2O)63+ is 1.4x10-4.
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43. Are solutions of the following salts acidic, basic, or neutral? For those that are not neutral, write balanced chemical equations
for the reactions causing the solution to be acidic or basic. (Ka (HNO2) = 4.0x10-4, Kb(C5H5N) = 1.7x10-9, Ka (NH4+) =
5.6x10-10, Ka (HClO) = 3.5x10-8)
a. NaNO3
b. NaNO2
c. C5H5NHClO4
d. NH4NO2
e. KOCl
f. NH4OCl
44. Place the species in each of the following groups in order of increasing acid strength. Explain the order you chose for each
group. a. HIO3, HBrO3
b. HNO2, HNO3
c. HOCl, HOI
d. H3PO4, H3PO3
45. Place the species in each of the following groups in order of increasing acid strength.
a. H2O, H2S, H2Se (bond energies: H-O, 467 kJ/mol; H-S, 363kJ/mol; H-Se, 276 kJ/mol
b. CH3CO2H, FCH2CO2H, F2CHCO2H, F3CCO2H
c. NH4+, HONH3+
d. NH4+, PH4+ (bond energies: N-H, 391kJ/mol; P-H, 322 kJ/mol)
46. Will the following oxides give acidic, basic, or neutral solutions when dissolved in water? Write reactions to justify your
answers.
a. CaO
b. SO2
c. Cl2O
47. Identify the Lewis acid and the Lewis base in each of the following reactions.
a. B(OH)3(aq) + H2O(l) ↔ B(OH)4-(aq) + H+(aq)
b. Ag+(aq) + 2NH3(aq) ↔ Ag(NH3)2+(aq)
c. BF3(g) + F-(aq) ↔ BF4-(aq)
48. Aluminum hydroxide is an amphoteric substance. It can act as either a Br Ønsted-Lowry base or as a Lewis acid. Write a
reaction showing Al(OH)3 acting as a base toward H+ and as an acid toward OH-.
49. Would you expect Fe3+ or Fe2+ to be a stronger Lewis acid? Explain.
WS#5: Buffers
50. A certain buffer is made by dissolving NaHCO3 and Na2CO3 in some water. Write equations to show how this buffer
neutralizes added H+ and OH-.
51. Calculate the pH of each of the following solutions.
a. 0.100M propanoic acid (HC3H5O2, Ka = 1.3x10-5)
b. 0.100M sodium propanoate (NaC3H5O2)
c. Pure H2O
d. A mixture containing 0.100M HC3H5O2 and 0.100M NaC3H5O2.
52. Compare the percent dissociation of the acid in (a) above with the percent dissociation of the acid in (d) above.
53. Calculate the pH after 0.020mol HCl is added to 1.00L of each of the four solutions in question 51.
54. Calculate the pH after 0.020mol NaOH is added to 1.00L of each of the four solutions in question 51.
55. Which of the solutions in question 51 shows the least change in pH upon addition of acid or base? Explain.
56. Calculate the pH of a solution that is 1.00M HNO2 and 1.00M NaNO2.
57. Calculate the pH after 0.10mol of NaOH is added to 1.00L of the solution in question 56, and calculate the pH after 0.20mol
of HCl is added to 1.00L of the solution in question 56.
58. Calculate the pH of each of the following buffered solutions.
a. 0.10M acetic acid/ 0.25M sodium acetate
d. 0.50M C2H5NH2/0.25M C2H5NH3Cl
b. 0.25M acetic acid/ 0.10M sodium acetate
e. 0.50M C2H5NH2/0.50M C2H5NH3
c. 0.25M acetic acid/ 0.25M sodium acetate
59. Calculate the pH after 0.010mol gaseous HCl is added to 250.0mL of each of the following buffered solutions.
a. 0.050M NH3/0.15M NH4Cl
b. 0.50M NH3/1.50M NH4Cl
Do the two original buffered solutions differ in their pH or their capacity? What advantage is there in having a buffer with a
great capacity?
60. Calculate the mass of sodium acetate that must be added to 500.0mL of 0.200M acetic acid to form a pH = 5.00 buffer
solution.
61. Consider a solution that contains both C5H5N and C5H5NHNO3. Calculate the ratio [C5H5N]/[ C5H5NH+] if the solution has
the following pH values.
A. 4.50
b. 5.00
c. 5.23
d. 5.50
62. Consider the acids in the above table. Which acid would be the best choice for preparing a pH= 7.00 buffer? Explain how to
make 1.0L of this buffer.
63. Which of the following mixtures would result in buffered solutions when 1.0L of each of the two solutions are mixed?
a. 0.1M KOH and 0.1M CH3NH3Cl
b. 0.1M KOH and 0.2M CH3NH2
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c. 0.2M KOH and 0.1M CH3NH3Cl
d. 0.1M KOH and 0.2M CH3NH3Cl
64. How many moles of NaOH must be added to 1.0L of 2.0M HC2H3O2 to produce a solution buffered at each pH?
a. pH = pKa
b. pH = 4.00
c. pH = 5.00
WS#6: Acid-Base Titrations/Indicators
65. Consider the titration of a generic weak acid HA with a strong base that gives the following titration curve:
pH
10
15
20
25
On the curve, indicate the points that correspond 5to the
following:
a. The stoichiometric (equivalence) point
b. The region with maximum buffering.
c. pH = pKa
d. pH depends only on [HA]
e. pH depends only on [A-]
f. pH depends on the amount of excess strong base added
66. Consider the titration of 40.0mL of 0.200M HClO4 by 0.100M KOH. Calculate the pH of the resulting solution after the
following volumes of KOH have been added.
a. 0.0 mL
b. 10.0 mL
c. 40.0 mL
d. 80.0 mL
e. 100.0 mL
67. Consider the titration of 100.0mL of 0.100M H2NNH2 (Kb = 3.0x10-6) by 0.200M HNO3. Calculate the pH of the resulting
solution after the following volumes of HNO3 have been added.
a. 0.0 mL
b. 20.0 mL
c. 25.0 mL
d. 40.0 mL
e. 50.0 mL
f. 100.0 mL
68. A 25.0mL sample of 0.100M lactic acid (HC3H5O3, pKa = 3.86) is titrated with 0.100M NaOH solution. Calculate the pH
after the addition of 0.0 mL, 4.0 mL, 8.0 mL, 12.5 mL, 20.0 mL, 24.0 mL, 24.5 mL, 24.9 mL, 25.0 mL, 25.1 mL, 26.0 mL,
28.0 mL, and 30.0 mL of the NaOH. Plot the results of your calculations as pH versus milliliters of NaOH added.
69. Repeat the procedure in Question 68, but for the titration of 25.0mL of 0.100M NH3 (Kb = 1.8x10-5) with 0.100M HCl.
70. Calculate the pH at the halfway point and at the equivalence point for each of the following titrations.
a. 100.0mL of 0.10M HC7H5O2 (Ka = 6.4x10-5) titrated by 0.10M NaOH.
b. 100.0mL of 0.10M C2H5NH2 (Kb = 5.6x10-4) titrated by 0.20M HNO3.
c. 100.0mL of 0.50M HCl titrated by 0.25M NaOH.
71. A sample of a certain monoprotic weak acid was dissolved in water and titrated with 0.125M NaOH, requiring 16.00mL to
reach the equivalence point. During the titration, the pH after adding 2.00mL of NaOH was 6.912. Calculate Ka for the weak
acid.
72. Two drops of indicator HIn (Ka = 1.0x10-9), where HIn is yellow and In- is blue, are placed in 100.0mL of 0.10M HCl.
a. What color is the solution initially?
b. The solution is titrated with 0.10M NaOH. At what pH will the color change (yellow to greenish yellow) occur?
c. What color will the solution be after 200.0mL of NaOH has been added?
73. (In class) Looking at the chart on the overhead, which indicators could be used for the titrations in Questions 66 and 67? In
Questions 68 and 69? Estimate the pH of a solution in which bromocresol green is blue and thymol blue is yellow.
WS#7: Additional Problems
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74. A 10.0mL sample of an HCl solution has a pH of 2.000. What volume of water must be added to change the pH to 4.000?
75. A typical vitamin C tablet (Containing pure ascorbic acid, H2C6H6O6) weighs 500.mg. One vitamin C tablet is dissolved in
enough water to make 200.0mL of solution. Calculate the pH of this solution. Ascorbic acid is a diprotic acid.
(Ka1 = 7.9x10-5, Ka2 = 1.6x10-12)
76. Acrylic acid (CH2=CHCO2H) is a precursor for many important plastics. Ka is 5.6x10-5.
a. Calculate the pH of a 0.10M solution of acrylic acid.
b. Calculate the percent dissociation of a 0.10M solution of acrylic acid.
c. Calculate the pH of a 0.050M solution of sodium acrylate (NaC3H3O2).
77. The equilibrium constant Ka for the reaction Fe(H2O)63+(aq) + H2O(l) ↔ Fe(H2O)5(OH)2+(aq) + H3O+(aq) is 6.0x10-3.
a. Calculate the pH of a 0.10M solution of Fe(H2O)63+(aq).
b. Will a 1.0M solution of iron(II) nitrate have a higher or lower pH than a 1.0M solution of iron(III) nitrate? Explain.
78. Is an aqueous solution of NHSO4 acidic, basic, or neutral? What reaction occurs with water? Calculate the pH of a 0.10M
solution of NaHSO4.
79. Hemoglobin (abbreviated Hb) is a protein responsible for the transport of oxygen in the blood of mammals. Each hemoglobin
molecule contains four iron atoms that are the binding sites for O 2 molecules. The oxygen binding is pH dependent. The
relevant equilibrium reaction is HbH44+(aq) + 4O2(g) ↔ Hb(O2)4(aq) + 4H+(aq). Use Le Chateliers principle to answer the
following.
a. What form of hemoglobin, HbH44+ or Hb(O2)4, is favored in the lungs? What form is favored in the cells?
b. When a person hyperventilates, the concentration of CO2 in the blood is decreased. How does this affect the oxygenbinding equilibrium? How does breathing into a paper bag help counteract this effect?
c. When a person has suffered a cardiac arrest, injection of a sodium bicarbonate solution is given. Why is this
necessary?
80. Students are often surprised to learn that organic acids, such as acetic acid, contain –OH groups. Actually, all oxyacids
contain hydroxyl groups. Sulfuric acid, usually written as H 2SO4, has the structural formula SO2(OH)2, where S is the central
atom. Identify the acids whose structural formulas are shown below. Why do they behave as acids, while NaOH and KOH
are bases?
a. SO(OH)2
b. ClO2(OH)
c. HPO(OH)2
81. Derive an equation analogous to the Henderson-Hasselbalch equation but relating pOH and pKb of a buffered solution
composed of a weak base and its conjugate acid, such as NH 3 and NH4+.
82. You have the following reagents on hand:
Solids (pKa of Acid form is Given
Solutions
Benzoic acid (4.19)
5.0M HCl
Sodium acetate (4.74)
1.0M acetic acid (4.74)
Potassium fluoride (3.14)
2.6M NaOH
Ammonium chloride (9.26)
1.0M HOCl (7.46)
What combination of reagents would you use to prepare buffers at the following pH values?
a. 3.0
b. 4.0
c. 5.0
d. 7.0
e. 9.0
83. Calculate the value of the equilibrium constant for each of the following reaction in aqueous solution.
a. HC2H3O2 + OH1-↔ C2H3O21- + H2O
b. C2H3O21- + H+ ↔ HC2H3O2
c. HCl + NaOH ↔ NaCl + H2O
84. Calculate the volume of 1.50x10-2M NaOH that must be added to 500.0mL of 0.200M HCl to give a solution that has a pH of
2.15.
85. The active ingredient in aspirin is acetylsalicylic acid. A 2.51g sample of acetylsalicylic acid required 27.36mL of 0.5106M
NaOH for a complete reaction. Addition of 13.68mL of 0.5106M HCl to the flask containing the aspirin and the sodium
hydroxide produced a mixture with a pH = 3.48. Find the molar mass of the acetylsalicylic acid and its Ka value. State any
assumptions you must make to reach your answer.
86. A student intends to titrate a solution of a weak monoprotic acid with a sodium hydroxide solution but reverses the two
solutions and places the weak acid solution in the buret. After 23.75mL of the weak acid solution has been added to 50.0mL
of the 0.100M NaOH solution, the pH of the resulting solution is 10.50. Calculate the original concentration of the solution of
weak acid.
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Answer Key.
1.
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