Chapter 2 review

65. Consider a reaction that produces a significant amount of hydrogen ion and is to be carried out a pH 7. Only two acids are available for making the buffer solution. The pKa values for acids A and B are 6.3 and 7.3, respectively. Which acid would serve as the optimum buffer for this reaction? Or would carrying out the reaction in water simply serve as well? A. acid A B. acid B C. water D. both acids would be equally effective

acid A

19. Which of the following molecules will not form hydrogen bonds? A. CH4 B. NH3 C. H2O D. HF

CH4

12. Which of the following molecules has polar bonds but is itself not polar? A. NH3 B. CO2 C. CH4 D. H2O

CO2

16. Molecules which contain both hydrophilic and hydrophobic regions are: A. Amphipathic B. Detergents C. Able to form micelles D. Both amphipathic and detergents. E. All of these

all of these

7. The water molecule is polar because: A. Electrons are not distributed symmetrically in the molecule. B. The hydrogen atoms are found on one "side" of the molecule. C. Hydrogen is less electronegative than oxygen. D. The hydrogen atoms are found on one "side" of the molecule and hydrogen is less electronegative than oxygen. E. All of these are correct.

all of these are correct

3. Many of the properties of water can be accounted for by the fact that A. it is polar B. it forms hydrogen bonds C. it is a bent molecule D. all of these are true

all of these are true

28. Which of the following characteristics makes for a good hydrogen bond donor? A. a high electronegativity B. a nonbonding pair of electrons C. both of the above D. neither of the above

a high electronegativity

38. Which will dissociate most in water, a weak acid or a strong acid? A. A weak acid. B. A strong acid C. They should dissociate about the same. D. It's impossible to predict.

a strong acid

40. Which has the greater Ka, a weak acid or a strong acid? A. A weak acid. B. A strong acid C. They should dissociate about the same. D. It's impossible to predict.

a strong acid

41. Which has the greater pKa, a weak acid or a strong acid? A. A weak acid. B. A strong acid C. They should dissociate about the same. D. It's impossible to predict.

a weak acid

31. Which of the following is a true statement? A. most substances contract when they freeze. B. water expands when it freezes. C. hydrogen bonding is related to water's tendency to expand as it freezes. D. all of these are true

all of these are true

68. A buffer solution A. is used to control the pH of a solution B. contains at least 100 times more of a weak acid than its conjugate base C. contains at least 100 times less of a weak acid than its conjugate base D. always has a pH of 7

is used to control the pH of a solution

62. Which substance would be the best buffer at pH 8 if it had to be able to buffer against either acid or base? A. one with a pKa of 7 B. one with a pKa of 8 C. one with a pKa of 9 D. The pKa of a substance doesn't tell you whether it would be a good buffer at this pH.

one with a PKA of 8

9. Which of the following molecules is amphipathic? A. sodium chloride B. acetic acid C. benzene D. palmitic acid

palmitic acid

18. Hydrogen bonds A. play an important role in the solvent properties of water B. are not involved in protein structure C. play a role in the properties of DNA, but not of RNA D. give water a lower boiling point than expected

play an important role in the solvent properties of water

2. If atoms with greatly differing electronegativities form a bond, that bond will be A. polar. B. nonpolar. C. amphipathic. D. acidic.

polar

45. The pH of a solution of 0.04 M HCl is: A. 4 B. 1.4 C. 0.4 D. 0.04 E. The pH cannot be determined

1.4

61. The ratio of a weak acid and its conjugate base at the point of maximum buffering capacity is A. 1/1 B. 1/10 C. 10/1 D. no definite ratio is needed

1/1

43. A buffer solution at pH 10 has a ratio of [HA]/[A-] of 10. What is the pKa of the acid? A. 8 B. 9 C. 10 D. 11 E. 12

11

46. The pOH a solution of 0.04 M HCl is: A. 1.4 B. 10 C. 12.6 D. 13.6 E. The pOH cannot be determined

12.6

55. A solution at pH 7 contains a weak acid, HA. The pKa of the acid is 6.5. What is the ratio of [A-]:[HA]? A. 1:3 B. 1:1 C. 3:1 D. 10:1

3:1

26. What is the maximum number of hydrogen bonds a single water molecule can form? A. 1 B. 2 C. 3 D. 4 E. 5

4

64. If the pH of 1 liter of a 1.0 M carbonate buffer is 7.0, what is the molar ratio of H2CO3 to HCO3-? (pK = 6.37) A. 0.234 B. 4.27 C. 6.37 D. 7.00 E. 10.20

4.27

47. An HCl solution has a pH = 3. If you dilute 10 mL of the solution to 1000mL, the final pH will be: A. 1.0 B. 2.0 C. The pH does not change. D. 4.0 E. 5.0

5.0

50. Calculate the final pH of a solution made by the addition of 10 mL of a 0.5 M NaOH solution to 500 mL of a 0.4 M HA originally at pH = 5.0 (pKa = 5.0) Neglect the volume change. A. 6.10 B. 5.09 C. 7.00 D. 5.55

5.55

52. What is the pH of an acetic acid solution where the concentration of acetic acid is 2 mM and the concentration of sodium acetate is 20 mM. The pKa of acetic acid is 4.76. A. 5.76 B. 10.6 C. 12.6 D. 8.8

5.76

44. The dissociation constant for an acid is 1 ´ 10-6. What is its pKa? A. -6 B. 6 C. 0.6 D. -0.6

6

60. An ammonia buffer contains NH3:NH4+ in a ratio of 0.4 moles:0.6 moles (pK = 9.75). What will be the pH if you add 0.01 moles of HCl to this buffer? A. 8.98 B. 9.04 C. 9.25 D. 9.46 E. 9.52

8.98

59. Using the Henderson-Hasselbalch equation, calculate the pH of an ammonia buffer when the NH3:NH4+ ratio is 0.4 moles:0.6 moles. (pK = 9.75) A. 7.40 B. 9.07 C. 9.25 D. 9.43 E. 11.05

9.07

79. The main blood buffer system is A. H2CO3/HCO3- B. HCO3-/CO32- C. H2CO3/CO32- D. none of the above

A

78. Which of the following is not true? A. A buffer is a solution which maintains a solution at a neutral pH B. Buffer solutions are made to resist change in pH C. Zwitterion buffers are less likely to interfere with biological reactions than non-zwitterions D. HEPES is a zwitterion buffer

A buffer is a solution which maintains a solution at a neutral pH

69. The main intracellular buffer system is A. H3PO4/H2PO4- B. H2PO4-/ HPO42- C. HPO42-/PO43- D. H3PO4/PO43-

B

25. True hydrogen bonds can NOT form between hydrogen and this element: A. N B. F C. C D. O E. All of these elements can form hydrogen bonds

C

49. What is the pH of a solution with [H+] = 10 mM? A. 10 B. 1 C. 2 D. -2

C

48. If a solution has a pH = 9.6, the [H+] is A. 2.5 ´ 1010 B. 9.6 M C. 2.5 M D. 2.5 ´ 10-10 M E. 9.6 ´ 10-10 M

D

53. The ion product constant for water (Kw) is equal to: A. 1014 B. 107 C. 100 D. 10-7 E. 10-14

E

5. Which of the following is a correct listing of electronegativity values, from low to high? A. C, H, O, N B. N, H, O, C C. H, C, N, O D. H, C, O, N

H, C, N, O

8. Which of the following molecules is polar? A. CCl4 B. CH4 C. CO2 D. NH3 E. None of these molecules is polar.

NH3

6. Which of the following elements has the highest electronegativity? A. C B. H C. N D. O E. P

O

37. For an acid that undergoes this reaction: HA « H+ + A- Ka = A. [H+][A-]/[HA] B. [H+][HA]/[A-] C. [HA][A-]/[H+] D. [A-]/[HA][H+] E. [H+]/[HA][A-]

a

42. The dissociation constant for an acid with a pKa value of 6.0 is A. 1 ´ 10-6 B. -1 ´ 106 C. 1 ´ 106 D. -1 ´ 10-6

a

77. Buffers which lack biological activity and are unlikely to interfere with any biochemical reactions include: A. Tris. B. Hepes. C. Phosphate. D. Both Tris and HEPES. E. All of these.

both Tris and HEPES

27. Which of the following characteristics makes for a good hydrogen bond acceptor? A. a high electronegativity B. a nonbonding pair of electrons C. both of these D. neither of these

both of these

51. If a solution has a pH = 6, the [H+] is A. 6 M B. 106 M C. 10-6 M D. 0.6 M

c

11. Which of the following classes of compounds is hydrophobic? A. Table Salt B. Cholesterol C. Phosphate esters D. Cholesterol and phosphate esters. E. All of these are hydrophobic.

cholesterol

1. The tendency for an atom to attract electrons to itself in a chemical bond is called A. polarity. B. electronegativity. C. hydrophilicity D. electrophilicity.

electronegativity

14. A micelle is a structure which A. aggregates with other micelles in water. B. has its polar groups on the outside and non-polar groups on the inside when in water. C. explains how soaps and detergents work. D. has its polar groups on the outside and non-polar groups on the inside when in water and explains how soaps and detergents work. E. All of these are true.

has its polar groups on the outside and non-polar groups on the inside when in water and explain how soaps and detergents work

23. The non-covalent interaction below associated with the strongest force in aqueous solution is A. dipole-induced dipole B. hydrophobic interactions C. hydrogen bonding D. van der Waals forces

hydrogen bonding

20. How does the strength of hydrogen bonds compare with covalent bonds? A. Hydrogen bonds are much stronger than covalent bonds. B. Hydrogen bonds are much weaker than covalent bonds. C. Hydrogen bonds and covalent bonds have similar strengths. D. The question cannot be answered without knowing which covalent bonds are being referred to

hydrogen bonds are much weaker than covalent bonds

29. Hydrogen bonds explain which of the following properties of water? A. Water is a great solvent for all ionic and polar molecules. B. Water has high melting and boiling points for its small size. C. Ice expands when frozen. D. Both the abnormal melting and freezing points and that ice expands when frozen. E. Hydrogen bonds explain all of these properties.

hydrogen bonds explain all of these properties

13. Ionic compounds and polar covalent compounds tend to dissolve in water because of A. ion-dipole and dipole-dipole interactions B. dipole-induced dipole interactions C. van der Waals bonds D. hydrophobic interactions

ion-dipole and dipole-dipole interactions

39. Bases are A. proton donors. B. proton acceptors. C. hydrogen bond donors. D. hydrogen bond acceptors.

proton acceptors

15. The substance most likely to form a micelle is A. acetic acid B. sodium palmitate C. methyl alcohol D. acetone

sodium palmitate

32. Which of the following compounds is most likely to form a micelle? A. Acetic acid. B. Glucose. C. Glycerol. D. Sodium palmitate. E. Sodium phosphate.

sodium palmitate

4. Which of the following is true about ionic compounds? A. They are more likely to dissolve in non-polar solvents than covalent compounds. B. They always dissolve completely in water. C. They never dissolve in polar solvents. D. Some of them dissolve completely in water or other polar solvents, while others do not.

some of them dissolve completely in water or other polar solvents, while others do not

10. Which of the following classes of compounds is hydrophilic? A. Sugars B. Fatty acids C. Amino acids D. Sugars and amino acids. E. All of these

sugars and amino acids

24. Which of the following statements about hydrogen bonds is false? A. The donor is a hydrogen atom bonded to a less electronegative atom then hydrogen. B. The more linear the bond, the stronger the attraction. C. The acceptor must contain a non-bonded pair of electrons. D. It is a type of non-covalent bond.

the donor is a hydrogen atom bonded to a less electronegative atom then hydrogen

63. Buffering capacity refers to A. the effectiveness of commercial antacids B. the extent to which a buffer solution can counteract the effect of added acid or base C. the pH of a buffer solution D. the molecular weight of the substance used as a buffer

the extent to which a buffer solution can counteract the effect of added acid or base

58. Which of the following is true? A. The pH of a solution where the A- to HA ratio is 1 has a pH = pKa. B. If the pH does not equal the pKa, the solution is not a buffer. C. The best buffer for any experiment will always have a pH equal to the pKa. D. If a buffer has more weak acid than conjugate base, the pH will be higher than the pKa.

the pH of a solution where the A to HA ratio is 1 has a pH = PKA

54. In a titration of a weak acid by a strong base A. two equivalents of base are always needed to neutralize all the acid present B. the equivalence point cannot be defined exactly C. there is a region in which the pH changes slowly D. the equivalence point depends on the nature of the added base

there is a region in which the pH changes slowly

21. Which of the following is true regarding hydrogen bonds. A. They can only form between two different molecules B. They are important in protein folding but not DNA structure C. They are important in DNA structure but not protein folding D. They can be found within a single molecule

they can be found within a single molecule

76. Nonphysiological buffers such as HEPES and PIPES have come into common use because A. they are inexpensive B. they can be prepared much more easily than other buffers C. they have less tendency to interfere with reactions D. they contain nitrogen

they have less tendency to interfere with reactions

17. How do hydrogen bonds tend to affect the melting and boiling points of substances? A. They tend to increase both melting and boiling points. B. They tend to decrease both melting and boiling points. C. They tend to increase melting points and decrease boiling points. D. They tend to decrease melting points and increase boiling points. E. They do not have any affect on either melting or boiling points.

they tend to increase in both melting and boiling points

22. In a hydrogen bond A. three atoms lie in a straight line B. there is stronger bonding than in a covalent bond C. unpaired electrons play no role D. none of the above

three atoms lie in a straight line

30. Hydrogen bonds can only form when the hydrogen atom is involved in a polar bond. A. True B. False

true

57. The inflection point of the titration curve for a weak monoprotic acid is equal to its pKa A. True B. False

true

36. Is water an acid or a base? A. Water is an acid. B. Water is a base. C. Water is both an acid and a base. D. Water is neither an acid nor a base.

water is both an acid and a base

56. When does a weak acid buffer best? A. From one pH unit below its pKa to its pKa. B. From its pKa to one pH unit above its pKa. C. Within one pH unit of its pKa, both above and below. D. Weak acids do not make good buffers at all.

within one pH unit of its PKA both above and below