ORGANIC CHEMISTRY 7TH EDITION BY BROWN - TEST BANK

ORGANIC CHEMISTRY 7TH EDITION BY BROWN – TEST BANK

 

Instant Download – Complete Test Bank With Answers

 

 

Sample Questions Are Posted Below

 

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

 

 

ANS:  A

 

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

 

 

ANS:  D

 

3. Which of the following is the correct order of decreasing basicity (stronger base > weaker base)?

a.	NH3 > MeNH2 > H2O > HF
b.	MeNH2 > NH3 > MeOH > CH4
c.	NH3 > Me3N > H2O > MeOH
d.	CH3COONa > NaOH > NaOMe > NaNMe2

 

 

ANS:  B

 

4. Which of the following is the strongest acid?

a.	CH3CH3
b.	CH3NH2
c.	CH3OH
d.	CH3F

 

 

ANS:  C

 

5. Which of the following is the strongest acid?

a.	HCl
b.	HI
c.	HF
d.	HBr

 

 

ANS:  B

 

 

6. Which of the following is easiest to deprotonate?

a.	CH4
b.	CH3CH3
c.	CH2=CH2
d.	HCºCH

 

 

ANS:  D

 

7. Which of the following is the strongest acid?

a.	CH3OH
b.	CH3CHO
c.	CH3COCH3
d.	CH3COOH

 

 

ANS:  D

 

8. Which of the following is the strongest acid?

a.	CH3NH2
b.	CH3PH2
c.	CH3OH
d.	CH3SH

 

 

ANS:  D

 

9. Which of the following compounds is the strongest acid?

a.	HF
b.	H2O
c.	NH3
d.	CH4

 

 

ANS:  A

 

10. Which of the following compounds is the strongest acid?

a.	CH3OCH3
b.	CH3CH2OH
c.	CH3CHO
d.	CH3CO2H

 

 

ANS:  D

 

11. Which of the following compounds is the strongest acid?

a.	CH3COOH
b.	ClCH2COOH
c.	CH3CH2OH
d.	ClCH2CH2OH

 

 

ANS:  B

 

12. Which of the following compounds is the strongest acid?

a.	CH3COOH
b.	FCH2COOH
c.	ClCH2COOH
d.	BrCH2COOH

 

 

ANS:  B

 

 

13. Which of the following compounds is the strongest acid?

a.	CH4
b.	CH3CH3
c.	H2C=CH2
d.	HCºCH

 

 

ANS:  D

 

14. Which of the following compounds is the strongest acid?

a.	CF3OH
b.	CF3CH2 CH2OH
c.	CF3CH2 CH2 CH2OH
d.	CF3CH2 CH2 CH2CH2OH

 

 

ANS:  A

 

15. Which of the following compounds is the strongest acid?

a.	CH3CH2CH2COOH
b.	CH3CH2CHClCOOH
c.	CH3CHClCH2COOH
d.	ClCH2CH2CH2COOH

 

 

ANS:  B

 

16. Which of the following is the strongest base?

a.	NaOH
b.	NaCO3
c.	H2O
d.	CH3OH

 

 

ANS:  A

 

17. Which of the following is the strongest base?

a.	iodide anion, I–
b.	fluoride anion, F–
c.	bromide anion, Br–
d.	chloride anion, Cl–

 

 

ANS:  B

 

18. Which of the following anions is the strongest base?

a.	CH3COO–
b.	HO–
c.	NH2–
d.	Cl–

 

 

ANS:  C

 

19. Which of the following anions is the strongest base?

a.	NH2–
b.	NH3
c.	CH3CH=N–
d.	CH3CºN

 

 

ANS:  A

 

20. Which of the following compounds has the highest pK_a?

a.	SiH4
b.	H2S
c.	PH3
d.	HCl

 

 

ANS:  A

 

21. Which of the following compounds has the highest pK_a?

a.	NH3
b.	H2O
c.	HCl
d.	CH4

 

 

ANS:  D

 

22. Which of the following compounds has the lowest pK_a?

a.	H2O
b.	HBr
c.	NH3
d.	CH4

 

 

ANS:  B

 

23. Which of the following compounds has the lowest pK_a?

a.	H2O
b.	H2S
c.	H2Se
d.	H2Te

 

 

ANS:  D

 

24. Which of the following is present in the highest concentration upon dissolution of H₂SO₄ in water?

a.	H2SO4
b.	H+
c.	H3O+
d.	HO–

 

 

ANS:  C

 

25. Which of the following is present in the highest concentration upon dissolution of acetic acid in water?

a.	OH–
b.	H3O+
c.	CH3COOH
d.	CH3COOH+

 

 

ANS:  C

 

26. Which of the following terms describes the reactivity of boron tribromide, BBr₃?

a.	Brønsted-Lowry acid and Lewis acid
b.	Brønsted-Lowry base and Lewis base
c.	Lewis acid and not a Brønsted-Lowry acid
d.	Lewis base and not a Brønsted-Lowry base

 

 

ANS:  C

 

 

27. Which of the following terms describes the reactivity of trimethylamine, (CH₃)₃N?

a.	Brønsted-Lowry acid and Lewis acid
b.	Brønsted-Lowry base and Lewis base
c.	Lewis acid and not a Brønsted-Lowry acid
d.	Lewis base and not a Brønsted-Lowry base

 

 

ANS:  B

 

28. Which set of curved arrows accounts for the deprotonation of an acid (A-H) by a base (:B)?

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  B

 

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

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  D

 

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

 

 

a.	Brønsted-Lowry acid
b.	Brønsted-Lowry base
c.	Lewis acid
d.	Lewis base

 

 

ANS:  B

 

 

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

 

 

a.	Brønsted-Lowry acid
b.	Brønsted-Lowry base
c.	Lewis acid
d.	Lewis base

 

 

ANS:  B

 

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

 

 

a.	Brønsted-Lowry acid
b.	Brønsted-Lowry base
c.	Lewis acid
d.	Lewis base

 

 

ANS:  A

 

33. Which of the following terms describes the role of ethyne in the acid-base reaction shown?

 

 

a.	Brønsted-Lowry acid
b.	Brønsted-Lowry base
c.	Lewis acid
d.	Lewis base

 

 

ANS:  A

 

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

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  D

 

 

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

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  D

 

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

 

 

ANS:  A

 

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

 

 

ANS:  B

 

38. Which of the following is a Lewis acid but not a Brønsted-Lowry acid?

a.	CH3COOH
b.	AlCl3
c.	H2O
d.	CH3OH

 

 

ANS:  B

 

39. Which of the following is a feature of a Lewis acid?

a.	proton donor
b.	proton acceptor
c.	electron pair donor
d.	electron pair acceptor

 

 

ANS:  D

 

40. Which of the following is a feature of a Lewis base?

a.	proton donor
b.	proton acceptor
c.	electron pair donor
d.	electron pair acceptor

 

 

ANS:  C

 

41. Which of the following is a feature of a Brønsted-Lowry acid?

a.	proton donor
b.	proton acceptor
c.	electron pair donor
d.	electron pair acceptor

 

 

ANS:  A

 

42. Which of the following is a feature of a Brønsted-Lowry base?

a.	proton donor
b.	proton acceptor
c.	electron pair donor
d.	electron pair acceptor

 

 

ANS:  B

 

43. Which of the following has the highest bond dissociation energy?

a.	HF
b.	HCl
c.	HBr
d.	HI

 

 

ANS:  A

 

44. Which of the following concepts can be used to rationalize the observation that acetic acid is a stronger acid than methanol?

a.	electronegativity
b.	resonance
c.	valence shell electron pair repulsion theory
d.	Pauli exclusion principle

 

 

ANS:  B

 

45. Which atom in the following structure is preferentially protonated by a strong acid?

 

 

a.	i
b.	ii
c.	iii
d.	iv

 

 

ANS:  A

 

 

46. What is the approximate pK_a value of HCl?

a.	-7
b.	5
c.	16
d.	51

 

 

ANS:  A

 

47. What is the approximate pK_a value of acetic acid?

a.	-7
b.	5
c.	16
d.	51

 

 

ANS:  B

 

48. Which of the following has a pK_a value of approximately 16?

a.	HBr
b.	CH3COOH
c.	CH3CH2OH
d.	HCºCH

 

 

ANS:  C

 

49. Which of the following has a pK_a value of approximately 25?

a.	CH3CH3
b.	CH2=CH2
c.	HCºCH
d.	CH3CH2OH

 

 

ANS:  C

 

50. Which of the following statements is not true?

a.	The position of the equilibrium for an exergonic reaction favors products
b.	The products of an exergonic reaction have a higher Gibbs free energy than the reactants.
c.	The equilibrium constant of a reaction for which DG° = 0 is 1.
d.	DG° = DH° – TDS°

 

 

ANS:  B

 

51. Which of the following equations is correct?

a.	DG° = DH° – TDS°
b.	DH° = DG° – TDS°
c.	DG° = DH° – DS°
d.	DG° = DH° – DS°/T

 

 

ANS:  A

 

 

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

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  B

 

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

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  D

 

54. Which of the following is a definition of the rate-determining step of a reaction mechanism?

a.	the first step
b.	the last step
c.	the step that crosses the highest energy barrier
d.	the most exothermic step

 

 

ANS:  C

 

55. Which of the following is a definition of the activation energy of a reaction?

a.	the difference in Gibbs free energy between the reactants and the transition state
b.	the difference in Gibbs free energy between the reactants and the intermediate
c.	the difference in Gibbs free energy between the reactants and the product
d.	the difference in Gibbs free energy between the transition state and the product

 

 

ANS:  A

 

 

56. Under which of the following conditions will a reaction be spontaneous when DH° > 0?

a.	TDS° = 0
b.	–TDS° > DH°
c.	TDS° < 0°
d.	DG° = 0

 

 

ANS:  B

 

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

 

 

a.	1
b.	2
c.	3
d.	4

 

 

ANS:  A

 

TRUE/FALSE

 

1. An acid with a low pK_a is a strong acid and has a weak conjugate base.

 

ANS:  T

 

2. In the following list,  there are four Lewis acids,  CH₃OH, HCl, BCl₃ and FeBr₃.

 

ANS:  T

 

3. In the following list, there are two organic Lewis bases.

 

ANS:  F

 

 

4. The following correctly shows the electron flow for the given reaction.

 

ANS:  T

 

5. Indole is pleasant smelling in highly dilute solutions and has been used in perfumery.

 

When indole is placed in the presence of a strong base the nitrogen atom will be deprotonated.

 

ANS:  T

 

6. Indole is pleasant smelling in highly dilute solutions and has been used in perfumery.

 

Indole can be classified as a Brønsted-Lowry base but not as a Lewis base..

 

ANS:  F

 

7. The following is generic depiction of a reaction using the curve arrow formalism.

 

 

In this reaction electrons move from C to B and A will have a positive charge in the product.

 

ANS:  F

 

8. The structure of the alkaloid ephedrine is shown below.  When ephedrine is placed in the presence of an acid,   the —OH group will be protonated.

 

 

ANS:  F

 

 

9. Consider the following reaction coordinate diagram.

This reaction is endergonic.

 

ANS:  F

 

10. Consider the following reaction coordinate diagram.

The transition state is represented by the letter B.

 

ANS:  T

 

11. Consider the following reaction coordinate diagram.

The free energy of activation is represented by the letter C.

 

ANS:  F

 

 

COMPLETION

 

Consider the acidity constants below to answer the following question(s).

 

ACID	STRUCTURE	pKa
phenol		10.00
ethanol	CH3CH2OH	16.00
water	HOH	15.74

 

 

1. Which acid will be almost completely deprotonated by NaOH?

 

ANS:  phenol

 

2. Which acid has the strongest conjugate base?

 

ANS:  ethanol

 

3. Which acid has the smallest K_a?

 

ANS:  ethanol

 

Consider the following terms.   Use these as appropriate to complete the following statements.

 

transition state

endergonic

exergonic

free energy of activation

Gibbs free energy changes

reaction intermediate

 

4. A species that lies at an energy maximum during an individual step in a reaction is termed ____________________.

 

ANS:  transition state

 

5. The energy needed by reactants to reach the transition state is the____________________,

 

ANS:  free energy of activation

 

6. A reaction where DG° is positive is _____________.

 

ANS:  endergonic

 

7. ____________________ is defined by the following equation.

 

DG° = –RT ln K_eq

 

ANS:  Gibbs free energy change

 

8. A reaction in which the free energy of the products is greater than the reactants is termed____________________ .

 

ANS:  endergonic

 

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.

 

 

ANS:

 

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.

 

 

ANS:

 

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.

 

 

ANS:

 

 

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.

 

 

ANS:

 

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

 

 

ANS:

 

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

 

ANS:

 

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

 

ANS:  K_a =  [H₂O] K_eq

 

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

 

ANS:  pK_a = –log₁₀K_a

 

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

 

ANS:  log₁₀K_eq = pK_a(acid) – pK_a(conjugate acid) = -8 – (-1.74) = -6.26

K_eq = 10^-6.26 = 5.5 x 10^-7

 

 

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

 

ANS:  log₁₀K_eq = pK_a(acid) – pK_a(conjugate acid) = -4.76 – (-1.74) = -3.02

K_eq = 10^-3.02 = 9.5 x 10^-4

 

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

 

ANS:  log₁₀K_eq = pK_a(acid) – pK_a(conjugate acid) = 25 – 15.7 = 9.3

K_eq = 10^9.3 = 2.0 x 10⁹

 

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

 

ANS:  log₁₀K_eq = pK_a(acid) – pK_a(conjugate acid) = 25 – 38 = 13             K_eq = 10¹³

 

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

 

ANS:  This trend is best understood in terms of the stability of the conjugate base that would be formed upon deprotonation of each of these acids. The methoxide anion (CH₃O^–), the conjugate base of methanol, has a negative charge on a highly electronegative oxygen atom. The oxygen atom accommodates the negative charge better than the nitrogen atom or carbon in the conjugate bases of methylamine and ethane (CH₃NH^– and CH₃CH₂^–, respectively).

 

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

 

ANS:  This trend is best understood in terms of the stability of the conjugate base that would be formed upon deprotonation of each of these acids. One explanation is that the negative charge of the acetate anion (CH₃CO₂^–), the conjugate base of acetic acid, is delocalized over the two oxygen atoms by resonance. In contrast, in the ethoxide anion (CH₃CH₂O^–), the conjugate base of ethanol, the negative charge is localized on a single oxygen atom.

 

 

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

 

ANS:  This trend is best understood in terms of the stability of the conjugate base that would be formed upon deprotonation of each of these acids. The highly electronegative fluorine atoms of the 2,2,2-trifluoroethoxide anion (CF₃CH₂O^–), the conjugate base of 2,2,2-trifluoroethanol, withdraw electron density from the oxygen atom and thereby stabilize the anion relative to the ethoxide anion (CH₃CH₂O^–), the conjugate base of ethanol.

 

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

 

CH₃CH₃         >         CH₂=CH₂         >         HCCH

ethane                        ethene                        ethyne

(ethylene)                  (acetylene)

51                              44                              25

 

ANS:  This trend is best understood in terms of the stability of the conjugate base that would be formed upon deprotonation of each of these acids. The lone pair of electrons of the acetylide anion (HCC^–) are in a lower-energy atomic orbital (an sp orbital), and more tightly held, than the lone pair of electrons in the conjugate bases of ethylene (H₂C=CH^–, sp² hybridized) and ethane (CH₃CH₂^–, sp³ hybridized), respectively.

 

 

 

17. Use curved arrows to show the movement of pairs of electrons in the following reaction between a Lewis acid and a Lewis base, and show the structure of the product.

 

 

ANS:

 

18. Use curved arrows to show the movement of pairs of electrons in the following reaction between a Lewis acid and a Lewis base, and show the structure of the product.

 

 

ANS: