Sabtu, 01 Agustus 2009

BUFFER SOLUTION QUIZ

1. Of the following mixtures, _____ is a buffer solution.
a. 1.0 M NH3/1.0 M NH4Cl
b. 1.0 M HCl/1.0 M NaCl
c. 1.0 M NaOH/1.0 M NaCl
d. 1.0 M KCl/1.0 M KOH
e. 1.0 M H2SO4/1.0 M K2SO4
2. A buffer solution may be prepared by using a weak acid and a salt containing ….
a. anion
b. cation
c. anion and cation
d. its conjugate base
e. its conjugate acid
3. A(n) _____ solution is one that resists change in pH when an acid or base is added to it.
a. buffered
b. acid
c. salt
d. aqueous
e. base
4. Of the following mixtures, _____ is a buffer solution.
a. 1.0 M NaOH/1.0 M NaCl
b. 1.0 M HCl/1.0 M NaCl
c. 1.0 M HF/1.0 M KF
d. 1.0 M KCl/1.0 M CH3COOH
e. 1.0 M HNO3/1.0 M KNO3
5. A buffer solution must contain (at least) ….
a. An acid and a base.
b. Any acid salt.
c. Water and a metal ion.
d. A conjugate pair containing at least one weak acid or one weak base.
e. Only a base salt.
6. Which of the following combinations will produce a buffer solution?
a. HCl and Cl-
b. NaCl and NaOH
c. SO42- and SO32-
d. HC2H302 and NaC2H3O2
e. HNO3 and HCl.
7. The Ka values for HF and HNO2 are 6.8 x 10-4 and 4.5 x 10-4 respectively. Therefore it follows the HF is a _____ acid than HNO2 and F- is a _____ base than NO2-.
a. weaker, stronger
b. stronger, stronger
c. stronger, weaker
d. weaker, weaker
8. The Ka values for HSO4- and H2PO4- are 1.2 x 10-2 and 6.3 x 10-8 respectively. Therefore it follows the HSO4- is a _____ acid than H2PO4- and SO42- is a _____ base than HPO42-.
a. weaker, weaker
b. weaker, stronger
c. stronger, weaker
d. stronger, stronger
9. alues for HPO42- and HSO3- are 4.8 x 10-13 and 6.3 x 10-8 respectively. Therefore it follows the HPO42- is a _____ acid than HSO3- and PO43- is a _____ base than SO32-
a. stronger, weaker
b. weaker, weaker
c. weaker, stronger
d. stronger, stronger
10. What change will occur for the following reaction if a few drops of HCl are added?
CH3CO2H + H2O
CH3CO2- + H3O+
a. a decrease in the fraction of acid dissociated
b. an increase in the fraction of acid dissociated
c. no change in the fraction of acid dissociated
11. What change will be observed for the following reaction if a few drops of NaOH are added?
HNO2 + H2O NO2- + H3O+
a. an increase in the fraction of acid dissociated
b. a decrease in the fraction of acid dissociated
c. no change in the fraction of acid dissociated
12. What change will occur for the following reaction if the hypochlorous acid solution is diluted from 0.1 to 0.01 M?
HOCl + H2O OCl- + H3O+
a. an increase in the fraction of acid dissociated
b. a decrease in the fraction of acid dissociated
c. no change in the fraction of acid dissociated
13. What is the hydronium ion concentration of a solution of 0.480 M acid and 0.680 M of its conjugate base if the ionization constant is 5.78 x 10-7?
a.2.77 x 10-7
b.3.93 x 10-6
c.8.19 x 10-9
d.4.08 x 10-7
e.8.50 x 10-7
14. What is the hydronium ion concentration of a solution of 0.700 M acid and 0.440 M of its conjugate base if the ionization constant is 3.59 x 10-8?
a. 8.98 x 10-8
b. 2.47 x 10-7
c. 1.13 x 10-7
d. 5.71 x 10-8
e. 2.26 x 10-8
15. What is the hydronium ion concentration of a solution of 0.720 M acid and 0.240 M of its conjugate base if the ionization constant is 4.38 x 10-6?
a. 6.08 x 10-6
b. 1.05 x 10-6
c. 3.15 x 10-5
d. 1.31 x 10-5
e. 1.46 x 10-6
16. What is the pH of a solution of 0.81 M acid and 0.35 M of its conjugate base if the ionization constant is 5.45 x 10-8?
a. 6.42
b. 6.70
c. 7.33
d. 6.90
e. 7.63
17. What is the hydronium ion concentration of a solution of 0.720 M acid and 0.240 M of its conjugate base if the ionization constant is 4.38 x 10-6?
a. 6.08 x 10-6
b. 1.05 x 10-6
c. 3.15 x 10-5
d. 1.31 x 10-5
e. 1.46 x 10-6
18. What is the pH of a solution of 0.81 M acid and 0.35 M of its conjugate base if the ionization constant is 5.45 x 10-8?
a.6.42
b.6.70
c.7.33
d.6.90
e.7.63
19. What is the pH of a solution of 0.28 M acid and 0.73 M of its conjugate base if the ionization constant is 3.75 x 10-9?
a.9.58
b.9.32
c.9.12
d.8.84
e.8.01
20. What is the pH of a solution of 0.49 M acid and 0.29 M of its conjugate base if the ionization constant is 5.92 x 10-8?
a.7.98
b.8.21
c.7.72
d.7.00
e.7.46
21. What is the pH of a solution of 0.17 M acid and 0.81 M of its conjugate base if the pKa = 8.62?
a.9.68
b.8.58
c.7.94
d.9.30
e.9.52
22. What is the pH of a solution of 0.28 M acid and 0.54 M of its conjugate base if the pKa = 7.93?
a.7.40
b.7.65
c.7.00
d.8.21
e.7.22
23. What is the pH of a solution of 0.65 M acid and 0.51 M of its conjugate base if the pKa = 5.30?
a.5.85 d. 5.41
b.6.05 e. 5.19
c.5.62
24. The toxic compound 2,4-dinitrophenol (used in biological research to inhibit energy production in cells) has Ka = 1.1 x 10-4 M. In an experiment, a solution of 2,4-dinitrophenol was prepared with the pH adjusted to 7.40. Calculate the ratio of the concentrations of the dissociated ion to the undissociated acid.
a. 1.2 x 102
b. 3.2 x 103
c. 1.4 x 101
d. 2.8 x 103
e. 4.7 x 103
25. Acetylsalicylic acid (aspirin) can have a serious effect on the stomach. Only the undissociated acid can cross the stomach lining. Calculate the ratio of acid to dissociated ion when the pH of the stomach is 2.00. The Ka of this acid is 2.75x10-5.
a.4.8 x 102 d. 35
b.1.2 x 102 e. 3.6 x 102
c.52
26. Uric acid is one metabolic end product and is excreted from the body in urine. The acid dissociation constant of uric acid is Ka = 4.0 x 10-6 M. The pH of a urine sample is 6.00. What is the ratio of urate ion to uric acid in the urine?
a.24
b.1.5
c.6.0
d.4.0
e.0.25
27. A buffer solution is prepared by the addition of 20.0 grams of HF and 21.0 grams of NaF to enough water to make 1.000 L of solution. The Ka of HF is 7.2 x 10-4. What is the pH of this solution?
a. 3.44
b. 3.14
c. 2.84
d. 7.0
e. 2.4
28. Which of the following pairs of compounds dissolved together in aqueous solution would NOT make a good buffer solution?
a. HNO3/NaNO3
b. H3PO4/NaH2PO4
c. H2CO3/KHCO3
d. HCN/KCN
29. We desire to make a buffer solution with a pH of 9.2. Which combination of compounds would be the best to use? Refer to the table of bases given.
a. HAc/NaAc
b. NH3/NH4Cl
c. HCl/NaCl
d. pyridine/pyridine chloride
30. A solution is prepared which is 1.0 M acetic acid. What would happen to the pH of this solution if potassium acetate were added to the solution?
a. pH would go up
b. pH would go down
c. would not affect the pH
31. An aqueous solution of NH3 is in equilibrium. Suppose a gram of NH4Cl is added to the solution, and it is allowed to come to a new equilibrium. What will happen to the pH as a result of addition of NH4Cl?
a. It will go down.
b. It will go up.
c. It will remain unaffected.
32. A buffer solution is 0.10 M HAc (acetic acid) and 0.10 M NaAc (sodium acetate) and we have 1.000 Liter of it.
What is the pH after 0.010 moles of HCl are added to this solution?
a. -2.0
b. 4.74
c. 4.82
d. 2.0
e. 4.65
33. A buffer solution has a pH = 5.5. What is the [H3O+] concentration?
a. 5.5 M
b. 3.16 x 10-6 M
c. 3.2 x 105 M
d. 0.74 M
e. 3.2 x 10-3 M
34. An indicator symbolically given as HIn can be in two different forms: as HIn (red) or as In- (yellow). The pKa of the indicator is 4.0. What will be the color of the indicator in a solution which has a pH = 7?
a. red
b. yellow
c. a color intermediate between yellow and red
35. Calculate the pH of a solution which is formally 0.50 M HAc and 0.10 M NaAc.
a. -2.5
b. 4.74
c. 5.44
d. 2.52
e. 4.04
36. A solution is prepared which is 1.0 M HOCl and 1.0 M NaOCl. What is its pH?
a. 0.0
b. 3.72
c. 7.0
d. 7.45
37. A solution is prepared which is 1.0 M HCl and 1.0 M NaCl. What is its pH?
a. -1.0
b. 1.0
c. 0.0
d. 7.0
e. 4.74
38. A 1.00 Liter buffer solution is prepared which is 1.0 M in HAc and 1.0 M in NaAc. What would be the pH after 10.0 grams of NaOH were added to the solution?
a. 7.00
b. 4.74
c. 4.52
d. 5.74
e. 4.96
39. What is the H+(aq) concentration of 0.10 M NaAc(aq)?
a. 1.34 x 10-9 M
b. 7.45 x 10-6 M
c. 1.0 x 10-7 M
d. 1.34 x 10-3 M
e. 7.45 x 10-12 M
40. The indicator bromocresol green, given symbolically as HIn, can be in two different forms: as HIn the color of the indicator is yellow, as In- the color of the indicator is blue, and an equilmolar mixture of the two species is green. The Ka of the indicator is 2.5x10-5. What will be the color of the indicator in a solution which has a pH = 3.8?
a. colorless
b. green
c. blue
d. yellow
41. A solution is prepared in which 1.0 mole of NaNO2 and 1.5 moles of HNO2 are added to a liter of aqueous solution. What is the pH of this solution?
a. 3.17
b. 3.35
c. 3.52
d. 0.176
e. 0.176
42. Suppose 3.65 grams of HCl are added to the solution in #6. What will be the new pH of the solution?
a. 2.75
b. 3.35
c. 3.60
d. 3.24
e. 3.10
43. Which salt would produce a solution with a pH significantly greater than 7.0?
a. NH4Cl
b. NaOCl
c. KCl
d. NaI
e. K2SO4
44. What is the [H+] concentration of a 0.500 M solution of NaF?
a. 2.0 x 10-13 M
b. 1.0 x 10-9 M
c. 1.0 x 10-5 M
d. 4.0 x 10-9 M
e. 2.6 x 10-6 M
45. Calculate the pH of a solution which is 2.0 M NH3 and 2.0 M NH4Cl.
a. 2.22
b. 4.74
c. 7.0
d. 9.26
e. 11.77
46. What is the Kb of the NO2- species?
a. 3.35
b. 10.6
c. 4.5 x 10-4
d. 2.2 x 10-11
e. 1.0 x 10-14
47. A flask originally contains 100.0 mL of 0.500 M aqueous HAc solution. To this solution is added 50.0 mL of 0.400 M NaOH solution. Calculate the pH of the resulting solution.
a. 4.56
b. 4.74
c. 4.96
d. 4.34
e. 2.52
48. When a weak acid is titrated with a strong base the following pH curve is obtained. What is the approximate pKa of the weak acid?
a. 1
b. 3
c. 4
d. 7
e. 14

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