University of Alabama

CH 231

CHAPTER 4—ACIDS AND BASES

MULTIPLE CHOICE

1)The pK_a of HCl is ?7. What is the value of the equilibrium constant, K_eq, for the following equilibrium? [The concentration of water in a dilute aqueous solution is 55 M]

a.    1.8 ? 10⁵

b. 385

c.     1.8 ? 10^?5

d. ?1.8 ? 10⁵

2. The pK_a of acetic acid, CH₃COOH, is 4.76. What is the value of the equilibrium constant K_eq, for the following equilibrium? [The concentration of water in a dilute aqueous solution is 55 M]

a.    3.2 ? 10⁷

b. ?3.2 ? 10^?7

c.     ?3.2 ? 10⁷

d. 3.2 ? 10^?7

3. Which of the following is the correct order of decreasing basicity (stronger base > weaker base)?
   1. NH₃ > MeNH₂ > H₂O > HF
   2. MeNH₂ > NH₃ > MeOH > CH₄
   3. NH₃ > Me₃N > H₂O > MeOH
   4. CH₃COONa > NaOH > NaOMe > NaNMe₂
4. Which of the following is the strongest acid?
   1. CH₃CH₃
   2. CH₃NH₂
   3. CH₃OH
   4. CH₃F
5. Which of the following is the strongest acid?
   1. HCl
   2. HI
   3. HF
   4. HBr

6. Which of the following is easiest to deprotonate?
   1. CH₄
   2. CH₃CH₃
   3. CH₂=CH₂
   4. HC? CH
7. Which of the following is the strongest acid?
   1. CH₃OH
   2. CH₃CHO
   3. CH₃COCH₃
   4. CH₃COOH
8. Which of the following is the strongest acid?
   1. CH₃NH₂
   2. CH₃PH₂
   3. CH₃OH
   4. CH₃SH
9. Which of the following compounds is the strongest acid?
   1. HF
   2. H₂O
   3. NH₃
   4. CH₄
10. Which of the following compounds is the strongest acid?
    1. CH₃OCH₃
    2. CH₃CH₂OH
    3. CH₃CHO
    4. CH₃CO₂H
11. Which of the following compounds is the strongest acid?
    1. CH₃COOH
    2. ClCH₂COOH
    3. CH₃CH₂OH
    4. ClCH₂CH₂OH
12. Which of the following compounds is the strongest acid?
    1. CH₃COOH
    2. FCH₂COOH
    3. ClCH₂COOH
    4. BrCH₂COOH

13. Which of the following compounds is the strongest acid?
    1. CH₄
    2. CH₃CH₃
    3. H₂C=CH₂
    4. HC? CH
14. Which of the following compounds is the strongest acid?
    1. CF₃OH
    2. CF₃CH₂ CH₂OH
    3. CF₃CH₂ CH₂ CH₂OH
    4. CF₃CH₂ CH₂ CH₂CH₂OH
15. Which of the following compounds is the strongest acid?
    1. CH₃CH₂CH₂COOH
    2. CH₃CH₂CHClCOOH
    3. CH₃CHClCH₂COOH
    4. ClCH₂CH₂CH₂COOH
16. Which of the following is the strongest base?
    1. NaOH
    2. NaCO₃
    3. H₂O
    4. CH₃OH
17. Which of the following is the strongest base?
    1. iodide anion, I^?
    2. fluoride anion, F^?
    3. bromide anion, Br^?
    4. chloride anion, Cl^?
18. Which of the following anions is the strongest base?
    1. CH₃COO^?
    2. HO?
    3.  

18. 4. Cl?
19. Which of the following anions is the strongest base?
    1.  

1. 2. NH₃
   3. CH₃CH=N^?
   4. CH₃C? N

20. Which of the following compounds has the highest pK_a?
    1. SiH₄
    2. H₂S
    3. PH₃
    4. HCl
21. Which of the following compounds has the highest pK_a?
    1. NH₃
    2. H₂O
    3. HCl
    4. CH₄
22. Which of the following compounds has the lowest pK_a?
    1. H₂O
    2. HBr
    3. NH₃
    4. CH₄
23. Which of the following compounds has the lowest pK_a?
    1. H₂O
    2. H₂S
    3. H₂Se
    4. H₂Te
24. Which of the following is present in the highest concentration upon dissolution of H₂SO₄ in water?
    1. H₂SO₄
    2. H⁺
    3. H₃O⁺
    4. HO?
25. Which of the following is present in the highest concentration upon dissolution of acetic acid in water?
    1. OH?
    2. H₃O⁺
    3. CH₃COOH
    4. CH₃COOH⁺
26. Which of the following terms describes the reactivity of boron tribromide, BBr₃?
    1. Brønsted-Lowry acid and Lewis acid
    2. Brønsted-Lowry base and Lewis base
    3. Lewis acid and not a Brønsted-Lowry acid
    4. Lewis base and not a Brønsted-Lowry base

27. Which of the following terms describes the reactivity of trimethylamine, (CH₃)₃N?
    1. Brønsted-Lowry acid and Lewis acid
    2. Brønsted-Lowry base and Lewis base
    3. Lewis acid and not a Brønsted-Lowry acid
    4. Lewis base and not a Brønsted-Lowry base
28. Which set of curved arrows accounts for the deprotonation of an acid (A-H) by a base (:B)?

1. 1. 1
   2. 2
   3. 3
   4. 4

29. Which sets of curved arrows accounts for the protonation of propene with HI?

1. 1. 1
   2. 2
   3. 3
   4. 4

30. Which of the following terms describes the role of ethene in the acid-base reaction shown?

1. 1. Brønsted-Lowry acid
   2. Brønsted-Lowry base
   3. Lewis acid
   4. Lewis base

31. Which of the following terms describes the role of ethanol in the acid-base reaction shown?

31. 1. Brønsted-Lowry acid
    2. Brønsted-Lowry base
    3. Lewis acid
    4. Lewis base
32. Which of the following terms describes the role of ethanol in the acid-base reaction shown?

32. 1. Brønsted-Lowry acid
    2. Brønsted-Lowry base
    3. Lewis acid
    4. Lewis base
33. Which of the following terms describes the role of ethyne in the acid-base reaction shown?

33. 1. Brønsted-Lowry acid
    2. Brønsted-Lowry base
    3. Lewis acid
    4. Lewis base
34. Which species is the conjugate acid in the following acid-base reaction?

1. 1. 1
   2. 2
   3. 3
   4. 4

35. Which species is the conjugate acid in the following acid-base reaction?

1. 1. 1
   2. 2
   3. 3
   4. 4

36. What is the value of the equilibrium constant, K_eq, for the following reaction?

a.    10¹³

b. 10?13

c.     13

d.   ¹/₁₃

37. What is the value of the equilibrium constant, K_eq, for the following reaction?

a.    10⁹

b. 10?9

c.     9

d. ¹/₉

38. Which of the following is a Lewis acid but not a Brønsted-Lowry acid?
    1. CH₃COOH
    2. AlCl₃
    3. H₂O
    4. CH₃OH
39. Which of the following is a feature of a Lewis acid?
    1. proton donor
    2. proton acceptor
    3. electron pair donor
    4. electron pair acceptor

40. Which of the following is a feature of a Lewis base?
    1. proton donor
    2. proton acceptor
    3. electron pair donor
    4. electron pair acceptor
41. Which of the following is a feature of a Brønsted-Lowry acid?
    1. proton donor
    2. proton acceptor
    3. electron pair donor
    4. electron pair acceptor
42. Which of the following is a feature of a Brønsted-Lowry base?
    1. proton donor
    2. proton acceptor
    3. electron pair donor
    4. electron pair acceptor
43. Which of the following has the highest bond dissociation energy?
    1. HF
    2. HCl
    3. HBr
    4. HI
44. Which of the following concepts can be used to rationalize the observation that acetic acid is a stronger acid than methanol?
    1. electronegativity
    2. resonance
    3. valence shell electron pair repulsion theory
    4. Pauli exclusion principle
45. Which atom in the following structure is preferentially protonated by a strong acid?

1. 1. i
   2. ii
   3. iii
   4. iv

46. What is the approximate pK_a value of HCl?
    1. ?7
    2. 5
    3. 16
    4. 51
47. What is the approximate pK_a value of acetic acid?
    1. ?7
    2. 5
    3. 16
    4. 51
48. Which of the following has a pK_a value of approximately 16?
    1. HBr
    2. CH₃COOH
    3. CH₃CH₂OH
    4. HC? CH
49. Which of the following has a pK_a value of approximately 25?
    1. CH₃CH₃
    2. CH₂=CH₂
    3. HC? CH
    4. CH₃CH₂OH
50. Which of the following statements is not true?
    1. The position of the equilibrium for an exergonic reaction favors products
    2. The products of an exergonic reaction have a higher Gibbs free energy than the reactants.
    3. The equilibrium constant of a reaction for which ? G? = 0 is 1.

d. ? G? = ? H? ? T? S?

51. Which of the following equations is correct?

a.    ? G? = ? H? ? T? S?

b.   ? H? = ? G? ? T? S?

c.     ? G? = ? H? ? ? S?

d. ? G? = ? H? ? ? S?/T

52. Which of the following energy diagrams represents the fastest reaction?

1. 1. 1
   2. 2
   3. 3
   4. 4

53. Which of the following energy diagrams represents the slowest reaction?

1. 1. 1
   2. 2
   3. 3
   4. 4

54. Which of the following is a definition of the rate-determining step of a reaction mechanism?
    1. the first step
    2. the last step
    3. the step that crosses the highest energy barrier
    4. the most exothermic step
55. Which of the following is a definition of the activation energy of a reaction?
    1. the difference in Gibbs free energy between the reactants and the transition state
    2. the difference in Gibbs free energy between the reactants and the intermediate
    3. the difference in Gibbs free energy between the reactants and the product
    4. the difference in Gibbs free energy between the transition state and the product

56. Under which of the following conditions will a reaction be spontaneous when ? H? > 0?
    1. T? S? = 0

b. ?T? S? > ? H?

c.     T? S? < 0?

d. ? G? = 0

57. Which of the following energy diagrams best represents the changes in energy during addition of HBr to an alkene?

1. 1. 1
   2. 2
   3. 3
   4. 4

PROBLEM

1. Use curved arrows to show the movement of pairs of electrons in the following acid-base reaction and show the structures of the conjugate acid and conjugate base.

2. Use curved arrows to show the movement of pairs of electrons in the following acid-base reaction and show the structures of the conjugate acid and conjugate base.

3. Complete the equation below for the protonation of 2-butene with HBr. Show the movement of pairs of electrons with curved arrows and provide the structures of the conjugate acid and conjugate base.

4. Complete the equation below for the protonation of cyclohexene with HCl. Show the movement of pairs of electrons with curved arrows and provide the structures of the conjugate acid and conjugate base.

5. Provide the equation for the equilibrium constant, K_eq, for the following equilibrium.

6. Provide the equation for the acid dissociate constant, K_a,for the following equilibrium.

7. Provide the equation that relates the equilibrium contant, K_eq, to the acid dissociation constant, K_a, for the following equilibrium.

8. Provide the equation that relates the acid dissociation constant, K_a, to the pK_a of an acid.

9. What is the value of the equilibrium constant for the following equilibrium?

10. What is the value of the equilibrium constant for the following equilibrium?

11. What is the value of the equilibrium constant for the following equilibrium?

12. What is the value of the equilibrium constant for the following equilibrium?

13. Provide a brief explanation, based on features of the molecules, for the following trend in pK_a values?

CH₃OH > CH₃NH₂ > CH₃CH₃ 16       38                     51

14. Provide a brief explanation, based on features of the molecules, for the following trend in pK_a values?

CH₃CH₂OH > CH₃COOH 15.9                            4.76

15. Provide a brief explanation, based on features of the molecules, for the following trend in pK_a values?

CH₃CH₂OH             >            CF₃CH₂OH

ethanol                   2,2,2-trifluoromethanol 15.9                                                 12.4