Name: Class: Date: AP 17.1-17.2 Study Questions True/False Indicate whether the statement is true or false. 1. The extent of ionization of a weak electrolyte is increased by adding to the solution a strong electrolyte that has an ion in common with the weak electrolyte. 2. For any buffer system, the buffer capacity depends on the amount of acid and base from which the buffer is made. Multiple Choice Identify the choice that best completes the statement or answers the question. 3. The ph of a solution that contains 0.818 M acetic acid (K a = 1.76 10-5 ) and 0.172 M sodium acetate is. a. 4.077 b. 5.434 c. 8.571 d. 8.370 e. 9.922 4. Calculate the ph of a solution that is 0.295 M in sodium formate (NaHCO 2 ) and 0.205 M in formic acid (HCO 2 H) The K a of formic acid is 1.77 10-4. a. 3.910 b. 3.587 c. 13.84 d. 10.10 e. 4.963 5. Calculate the percent ionization of formic acid (HCO 2 H) in a solution that is 0.311 M in formic acid and 0.189 M in sodium formate (NaHCO 2 ). The K a of formic acid is 1.77 10-4. a. 37.8 b. 0.0937 c. 11.3 d. 1.06 10-3 e. 3.529 6. Calculate the percent ionization of formic acid (HCO 2 H) in a solution that is 0.219 M in formic acid. The K a of formic acid is 1.77 10-4. a. 3.94 10-5 b. 0.0180 c. 2.84 d. 0.280 e. 12.2 7. Calculate the ph of a solution that is 0.210 M in nitrous acid (HNO 2 ) and 0.290 M in potassium nitrite (KNO 2 ). The acid dissociation constant of nitrous acid is 4.50 10-4. a. 3.487 b. 3.210 c. 13.86 d. 10.51 e. 4.562 8. Calculate the percent ionization of nitrous acid in a solution that is 0.222 M in nitrous acid (HNO 2 ) and 0.278 M in potassium nitrite (KNO 2 ). The acid dissociation constant of nitrous acid is 4.50 10 4. a. 55.6 b. 0.162 c. 15.5 d. 2.78 10-3 e. 3.448 9. Calculate the percent ionization of nitrous acid in a solution that is 0.249 M in nitrous acid. The acid dissociation constant of nitrous acid is 4.50 10 4. a. 1.12 10-4 b. 0.0450 c. 4.25 d. 0.342 e. 5.53 10. Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of fluoride ions after the addition of 5.00 ml of 0.0100 M HCl to 25.0 ml of this solution is M. a. 0.0850 b. 0.00167 c. 0.0980 d. 0.0817 e. 0.00253 11. Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of hydrogen fluoride after addition of 5.00 ml of 0.0100 M HCl to 25.0 ml of this solution is M. a. 0.107 b. 0.100 c. 0.126 d. 0.00976 e. 0.00193 1
Name: 12. The K a of acetic acid is 1.76 10-5. The ph of a buffer prepared by combining 50.0 ml of 1.00 M potassium acetate and 50.0 ml of 1.00 M acetic acid is. a. 1.705 b. 0.851 c. 3.406 d. 4.754 e. 2.383 13. The K b of ammonia is 1.77 10-5. The ph of a buffer prepared by combining 50.0 ml of 1.00 M ammonia and 50.0 ml of 1.00 M ammonium nitrate is. a. 4.63 b. 9.25 c. 4.74 d. 9.37 e. 7.00 14. Calculate the ph of a solution prepared by dissolving 0.370 mol of formic acid (HCO 2 H) and 0.230 mol of sodium formate (NaCO 2 H) in water sufficient to yield 1.00 L of solution. The K a of formic acid is 1.77 10 4. a. 2.099 b. 10.463 c. 3.546 d. 2.307 e. 3.952 15. Calculate the ph of a solution prepared by dissolving 0.750 mol of NH 3 and 0.250 mol of NH 4 Cl in water sufficient to yield 1.00 L of solution. The K b of ammonia is 1.77 10 5. a. 5.22 b. 4.27 c. 9.73 d. 8.78 e. 0.89 16. Calculate the ph of a solution prepared by dissolving 0.250 mol of benzoic acid (C 7 H 5 O 2 H) and 0.150 mol of sodium benzoate (NaC 7 H 5 O 2 ) in water sufficient to yield 1.00 L of solution. The K a of benzoic acid is 6.50 10 5. a. 4.411 b. 2.395 c. 3.965 d. 10.084 e. 4.190 17. Calculate the ph of a solution prepared by dissolving 0.150 mol of benzoic acid (HBz) and 0.300 mol of sodium benzoate in water sufficient to yield 1.00 L of solution. The K a of benzoic acid is 6.50 10 5. a. 2.516 b. 3.892 c. 4.488 d. 10.158 e. 4.195 18. The ph of a solution prepared by dissolving 0.350 mol of solid methylamine hydrochloride (CH 3 NH 3 Cl) in 1.00 L of 1.10 Mmethylamine (CH 3 NH 2 ) is. The K b for methylamine is 4.40 10 4. (Assume the final volume is 1.00 L.) a. 1.66 b. 2.86 c. 10.28 d. 11.14 e. 10.61 19. Which one of the following pairs cannot be mixed together to form a buffer solution? a. NH 3, NH 4 Cl b. NaC 2 H 3 O 2, HCl (C 2 H 3 O 2 - = acetate) c. RbOH, HBr d. KOH, HF e. H 3 PO 4, KH 2 PO 4 20. Which one of the following pairs cannot be mixed together to form a buffer solution? a. C 5 H 5 N, C 5 H 5 NHCl b. HC 2 H 3 O 2, NaOH (C 2 H 3 O 2 - = acetate) c. KOH, HI d. NH 2 CH 3, HCl e. NaClO, HNO 3 21. A solution containing which one of the following pairs of substances will be a buffer solution? a. NaI, HI b. KBr, HBr c. RbCl, HCl d. CsF, HF e. none of the above 22. What change will be caused by addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride? a. The concentration of hydronium ions will increase significantly. b. The concentration of fluoride ions will increase as will the concentration of hydronium ions. c. The concentration of hydrogen fluoride will decrease and the concentration of fluoride ions will increase. d. The concentration of fluoride ion will decrease and the concentration of hydrogen fluoride will increase. e. The fluoride ions will precipitate out of solution as its acid salt. 23. The Henderson-Hasselbalch equation is. a. [H + ] = K a + b. ph = pk a - log c. ph = pk a + log d. ph = pk a + log e. ph = log 2
Name: 24. In a solution, when the concentrations of a weak acid and its conjugate base are equal, a. the system is not at equilibrium. b. the buffering capacity is significantly decreased. c. the -log of the [H + ] and the -log of the K a are equal. d. all of the above are true. 25. Of the following solutions, which has the greatest buffering capacity? a. 0.821 M HF and 0.217 M NaF b. 0.821 M HF and 0.909 M NaF c. 0.100 M HF and 0.217 M NaF d. 0.121 M HF and 0.667 M NaF e. They are all buffer solutions and would all have the same capacity. 26. Of the following solutions, which has the greatest buffering capacity? a. 0.521 M HC 2 H 3 O 2 and 0.217 M NaC 2 H 3 O 2 b. 0.821 M HC 2 H 3 O 2 and 0.713 M NaC 2 H 3 O 2 c. 0.365M HC 2 H 3 O 2 and 0.497 M NaC 2 H 3 O 2 d. 0.121 M HC 2 H 3 O 2 and 0.116 M NaC 2 H 3 O 2 27. Of the following solutions, which has the greatest buffering capacity? a. 0.543 M NH 3 and 0.555 M NH 4 Cl b. 0.087 M NH 3 and 0.088 M NH 4 Cl c. 0.234 M NH 3 and 0.100 M NH 4 Cl d. 0.100 M NH 3 and 0.455 M NH 4 Cl e. They are all buffer solutions and would all have the same capacity. 28. The addition of hydrofluoric acid and to water produces a buffer solution. a. HCl b. NaNO 3 c. NaF d. NaCl e. NaBr 29. The addition of hydrochloric acid and to water produces a buffer solution. a. HC 6 H 5 O b. NaOH c. NH 3 d. HNO 3 e. NaNO 3 30. The addition of sodium hydroxide and to water produces a buffer solution. a. HCl b. NaC 2 H 3 O 2 c. NaF d. HC 7 H 5 O 2 e. NaCl 31. Which of the following could be added to a solution of sodium acetate to produce a buffer? a. acetic acid only b. acetic acid or hydrochloric acid c. hydrochloric acid only d. potassium acetate only e. sodium chloride or potassium acetate 32. Which of the following could be added to a solution of potassium fluoride to prepare a buffer? a. sodium hydroxide b. potassium acetate c. hydrochloric acid d. sodium fluoride e. ammonia 33. Which of the following could be added to a solution of acetic acid to prepare a buffer? a. sodium hydroxide b. hydrochloric acid c. nitric acid d. more acetic acid e. None of the above can be added to an acetic acid solution to prepare a buffer. 34. Which of the following could be added to a solution of acetic acid to prepare a buffer? a. sodium acetate only b. sodium acetate or sodium hydroxide c. nitric acid only d. hydrofluoric acid or nitric acid e. sodium hydroxide only 35. The primary buffer system that controls the ph of the blood is the buffer system. a. carbon dioxide, carbonate b. carbonate, bicarbonate c. carbonic acid, carbon dioxide d. carbonate, carbonic acid e. carbonic acid, bicarbonate 36. What are the principal organs that regulate the ph of the carbonic acid-bicarbonate buffer system in the blood? a. kidneys, liver b. lungs, kidneys c. spleen, liver d. lungs, skin e. brain stem, heart 37. Human blood is. a. neutral b. very basic c. slightly acidic d. very acidic e. slightly basic 3
Name: 38. Which one of the following will cause hemoglobin to release oxygen? a. increase in ph b. decrease in ph c. decrease in temperature d. decrease in CO 2 concentration e. increase in O 2 concentration 39. What is the ph of a buffer solution that is 0.211 M in lactic acid and 0.111 M in sodium lactate? The K a of lactic acid is 1.4 10-4. a. 14.28 b. 10.43 c. 5.48 d. 3.57 e. 4.13 40. What is the ph of a buffer solution that is 0.255 M in hypochlorous acid (HClO) and 0.333 M in sodium hypochlorite? The K a of hypochlorous acid is 3.8 10-8. a. 13.88 b. 6.46 c. 8.49 d. 7.30 e. 7.54 41. A solution is prepared by dissolving 0.23 mol of chloroacetic acid and 0.27 mol of sodium chloroacetate in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the ph to drop slightly. The ph does not decrease drastically because the HCl reacts with the present in the buffer solution. The K a of chloroacetic acid is 1.36 10-3. a. H 2 O b. H 3 O + c. chloroacetate ion d. chloroacetic acid e. This is a buffer solution: the ph does not change upon addition of acid or base. 42. A solution is prepared by dissolving 0.23 mol of hydrazoic acid and 0.27 mol of sodium azide in water sufficient to yield 1.00 L of solution.the addition of 0.05 mol of NaOH to this buffer solution causes the ph to increase slightly. The ph does not increase drastically because the NaOH reacts with the present in the buffer solution. The K a of hydrazoic acid is 1.9 10-5. a. H 2 O b. H 3 O + c. azide d. hydrazoic acid e. This is a buffer solution: the ph does not change upon addition of acid or base. Completion Complete each statement. 43. Calculate the ph of a buffer that contains 0.270 M hydrofluoric acid (HF) and 0.180 M cesium fluoride (CsF). The Ka of hydrofluoric acid is 6.80 10-4. 44. Calculate the ph of a buffer solution that contains 0.820 grams of sodium acetate and 0.010 moles of acetic acid in 100 ml of water. The Ka of acetic acid is 1.77 10-5. 4
AP 17.1-17.2 Study Questions Answer Section TRUE/FALSE 1. ANS: F PTS: 1 DIF: 2 REF: Sec. 17.1 2. ANS: T PTS: 1 DIF: 2 REF: Sec. 17.2 MULTIPLE CHOICE 3. ANS: A PTS: 1 DIF: 3 REF: Sec. 17.1 4. ANS: A PTS: 1 DIF: 3 REF: Sec. 17.1 5. ANS: B PTS: 1 DIF: 4 REF: Sec. 17.1 6. ANS: C PTS: 1 DIF: 4 REF: Sec. 17.1 7. ANS: A PTS: 1 DIF: 4 REF: Sec. 17.1 8. ANS: B PTS: 1 DIF: 4 REF: Sec. 17.1 9. ANS: C PTS: 1 DIF: 4 REF: Sec. 17.1 10. ANS: D PTS: 1 DIF: 5 REF: Sec. 17.2 11. ANS: A PTS: 1 DIF: 5 REF: Sec. 17.2 12. ANS: D PTS: 1 DIF: 4 REF: Sec. 17.2 13. ANS: B PTS: 1 DIF: 4 REF: Sec. 17.2 14. ANS: C PTS: 1 DIF: 4 REF: Sec. 17.2 15. ANS: C PTS: 1 DIF: 4 REF: Sec. 17.2 16. ANS: C PTS: 1 DIF: 4 REF: Sec. 17.2 17. ANS: C PTS: 1 DIF: 4 REF: Sec. 17.2 18. ANS: D PTS: 1 DIF: 4 REF: Sec. 17.2 19. ANS: C PTS: 1 DIF: 2 REF: Sec. 17.2 20. ANS: C PTS: 1 DIF: 2 REF: Sec. 17.2 21. ANS: D PTS: 1 DIF: 2 REF: Sec. 17.2 22. ANS: D PTS: 1 DIF: 3 REF: Sec. 17.2 23. ANS: C PTS: 1 DIF: 1 REF: Sec. 17.2 24. ANS: C PTS: 1 DIF: 3 REF: Sec. 17.2 25. ANS: B PTS: 1 DIF: 3 REF: Sec. 17.2 26. ANS: B PTS: 1 DIF: 3 REF: Sec. 17.2 27. ANS: A PTS: 1 DIF: 3 REF: Sec. 17.2 28. ANS: C PTS: 1 DIF: 1 REF: Sec. 17.2 29. ANS: C PTS: 1 DIF: 3 REF: Sec. 17.2 30. ANS: D PTS: 1 DIF: 3 REF: Sec. 17.2 31. ANS: B PTS: 1 DIF: 2 REF: Sec. 17.2 32. ANS: C PTS: 1 DIF: 2 REF: Sec. 17.2 33. ANS: A PTS: 1 DIF: 2 REF: Sec. 17.2 34. ANS: B PTS: 1 DIF: 2 REF: Sec. 17.2 35. ANS: E PTS: 1 DIF: 2 REF: Sec. 17.2 36. ANS: B PTS: 1 DIF: 3 REF: Sec. 17.2 1
37. ANS: E PTS: 1 DIF: 2 REF: Sec. 17.2 38. ANS: B PTS: 1 DIF: 3 REF: Sec. 17.2 39. ANS: D PTS: 1 DIF: 4 REF: Sec. 17.2 40. ANS: E PTS: 1 DIF: 4 REF: Sec. 17.2 41. ANS: C PTS: 1 DIF: 2 REF: Sec. 17.2 42. ANS: D PTS: 1 DIF: 2 REF: Sec. 17.2 COMPLETION 43. ANS: 2.99 PTS: 1 DIF: 3 REF: Sec. 17.2 44. ANS: 4.75 PTS: 1 DIF: 3 REF: Sec. 17.2 2