Question

1. The pH of a solution at 25°C in which [OH-] = 4.0 × 10-5 M is: 4.40 9.60 4.00 4.80 None of these choices are correct. 2. Calculate the pOH of a 6.0 M solution of HCl. -0.78 0.78 13.22 -0.90 14.78 3. What volume of water must be added to 14.5 mL of a pH 2.0 solution of HNO3 in order to change the pH to 4.0? 4.40 9.60 4.00 4.80 None of these choices are correct. 4. For nitrous acid, HNO2, Ka = 4*10^-4. Calculate the pH of 0.72 M HNO2. 1.77 0.14 3.54 12.23 None of these choices are correct. 5. Determine the concentration of a solution of the weak acid HClO2 (Ka = 1.10 × 10-2) if it has a pH of 2.000. 4.40 9.60 4.00 4.80 None of these choices are correct. 6. What concentration of acetic acid (Ka = 1.80 × 10-5) has the same pH as that of 6.30 × 10-3 M HCl? 6.30 × 10-3 M M 11.8 M 2.21 M None of these choices are correct. 7. Saccharin is a monoprotic acid. If the pH of a 5.20 × 10-3 M solution of this acid is 2.53, what is the Ka of saccharin? 1.7 × 10-3 3.9 × 10-3 8.7 × 10-6 2.9 × 10-3 None of these choices are correct. 8. A monoprotic weak acid when dissolved in water is 1.35% dissociated and produces a solution with a pH of 3.85. Calculate the Ka of the acid. Need to know the initial concentration of the acid. 1.4 × 10-2 1.9 × 10-6 × 10-2 None of these choices are correct. 9. Calculate the pH of the following aqueous solution: 0.90 M aniline (pKb = 9.42) 9.27 4.53 4.73 9.47 None of these choices are correct. 10. Given that the Ka for HOCl is 3.45 × 10-8, calculate the K value for the reaction of HOCl with OH-. 3.45 × 10-22 2.90 × 10-7 2.90 × 1021 3.45 × 106 3.45 11. Calculate the Ka for an unknown monoprotic acid HX, given that a solution of 1.20 M LiX has a pH of 8.90. 4.40 9.60 4.00 4.80 None of these choices are correct. 12. Ka for benzoic acid, C6H5COOH, is 6.30×10-5. Ka for hypochlorous acid, HClO, is 3.50×10-8. Ka for hydrocyanic acid, HCN, is 4.00×10-10. What is the formula for the weakest acid? 13. Calculate the [H+] in a solution that is 0.19 M in NaF and 0.25 M in HF. (Ka = 7.2 × 10-4) 9.5 × 10-4 M 7.2 × 10-4 M 0.20 M 5.5 × 10-4 M 1.3 M 14. 15.0 mL of 0.50 M HCl is added to a 100.-mL sample of 0.480 M HNO2 (Ka for HNO2 = 4.0 × 10-4). What is the equilibrium concentration of NO2- ions? 2.6 × 10-3 M 4.2 × 10-1 M 5.1 × 10-2 M 1.7 × 10-4 M None of these choices are correct 15. The following question refers to a 2.0-liter buffered solution created from 1.30 M NH3 (Kb = 1.8 × 10-5) and 0.26 M NH4F. When 0.10 mol of H+ ions is added to the solution what is the pH? 5.35 8.56 4.14 9.86 9.85 16. You have solutions of 0.200 M HNO2 and 0.200 M KNO2 (Ka for HNO2 = 4.00 × 10-4). A buffer of pH 3.000 is needed. What volumes of HNO2 and KNO2 are required to make 1 liter of buffered solution? 286 mL HNO2; 714 mL KNO2 714 mL HNO2; 286 mL KNO2 500 mL of each 587 mL HNO2; 413 mL KNO2 413 mL HNO2; 587 mL KNO2 17. The following question refers to the following system: A 1.0-liter solution contains 0.25 M HF and 1.30 M NaF (Ka for HF is 7.2 × 10-4). If one adds 0.30 liters of 0.020 M KOH to the solution, what will be the change in pH? 0.73 -0.08 3.87 0.01 -0.19 18. Consider the titration of 300.0 mL of 1.400 M NH3 (Kb = 1.8 × 10-5) with 0.500 M HNO3. After 150.0 mL of 0.500 M HNO3 have been added, the pH of the solution is: 11.92 9.92 4.08 6.92 None of these choices are correct. 19. A 75.0-mL sample of 0.0500 M HCN (Ka = 6.2 × 10-10) is titrated with 0.420 M NaOH. What is the [H+] in the solution after 3.0 mL of 0.420 M NaOH have been added? 2.0 M × 10-7 M 1.2 × 10-9 M 8.2 × 10-6 M None of these choices are correct. 20. Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range. Which indicator would be best for the following titration? 0.100 M HF (Ka = 7.2 × 10-4) + 0.100 M NaOH cresol red (7.0 - 8.8) crystal violet (0.2 - 1.8) phenolphthalien (8.2 - 10.0) bromothymol blue (6.0 - 7.6) erythosin B (2.2 - 3.5) 21. An aqueous solution contains 0.33 M nitrous acid. One Liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) 0.166 mol KOH 0.34 mol NaNO2 0.17 mol HI 0.33 mol NaI 0.34 mol HI

          1. The pH of a solution at 25°C in which [OH-] = 4.0 × 10-5 M is:
4.40
9.60
4.00
4.80
None of these choices are correct.

2. Calculate the pOH of a 6.0 M solution of HCl.
-0.78
0.78
13.22
-0.90
14.78

3. What volume of water must be added to 14.5 mL of a pH 2.0 solution of HNO3 in order to change the pH to 4.0?
4.40
9.60
4.00
4.80
None of these choices are correct.

4. For nitrous acid, HNO2, Ka = 4*10^-4. Calculate the pH of 0.72 M HNO2.
1.77
0.14
3.54
12.23
None of these choices are correct.

5. Determine the concentration of a solution of the weak acid HClO2 (Ka = 1.10 × 10-2) if it has a pH of 2.000.
4.40
9.60
4.00
4.80
None of these choices are correct.

6. What concentration of acetic acid (Ka = 1.80 × 10-5) has the same pH as that of 6.30 × 10-3 M HCl?
6.30 × 10-3 M
M
11.8 M
2.21 M
None of these choices are correct.

7. Saccharin is a monoprotic acid. If the pH of a 5.20 × 10-3 M solution of this acid is 2.53, what is the Ka of saccharin?
1.7 × 10-3
3.9 × 10-3
8.7 × 10-6
2.9 × 10-3
None of these choices are correct.

8. A monoprotic weak acid when dissolved in water is 1.35% dissociated and produces a solution with a pH of 3.85. Calculate the Ka of the acid.
Need to know the initial concentration of the acid.
1.4 × 10-2
1.9 × 10-6
× 10-2
None of these choices are correct.

9. Calculate the pH of the following aqueous solution:
0.90 M aniline (pKb = 9.42)
9.27
4.53
4.73
9.47
None of these choices are correct.

10. Given that the Ka for HOCl is 3.45 × 10-8, calculate the K value for the reaction of HOCl with OH-.
3.45 × 10-22
2.90 × 10-7
2.90 × 1021
3.45 × 106
3.45

11. Calculate the Ka for an unknown monoprotic acid HX, given that a solution of 1.20 M LiX has a pH of 8.90.
4.40
9.60
4.00
4.80
None of these choices are correct.

12. Ka for benzoic acid, C6H5COOH, is 6.30×10-5. Ka for hypochlorous acid, HClO, is 3.50×10-8. Ka for hydrocyanic acid, HCN, is 4.00×10-10. What is the formula for the weakest acid?

13. Calculate the [H+] in a solution that is 0.19 M in NaF and 0.25 M in HF. (Ka = 7.2 × 10-4)
9.5 × 10-4 M
7.2 × 10-4 M
0.20 M
5.5 × 10-4 M
1.3 M

14. 15.0 mL of 0.50 M HCl is added to a 100.-mL sample of 0.480 M HNO2 (Ka for HNO2 = 4.0 × 10-4). What is the equilibrium concentration of NO2- ions?
2.6 × 10-3 M
4.2 × 10-1 M
5.1 × 10-2 M
1.7 × 10-4 M
None of these choices are correct

15. The following question refers to a 2.0-liter buffered solution created from 1.30 M NH3 (Kb = 1.8 × 10-5) and 0.26 M NH4F. When 0.10 mol of H+ ions is added to the solution what is the pH?
5.35
8.56
4.14
9.86
9.85

16. You have solutions of 0.200 M HNO2 and 0.200 M KNO2 (Ka for HNO2 = 4.00 × 10-4). A buffer of pH 3.000 is needed. What volumes of HNO2 and KNO2 are required to make 1 liter of buffered solution?
286 mL HNO2; 714 mL KNO2
714 mL HNO2; 286 mL KNO2
500 mL of each
587 mL HNO2; 413 mL KNO2
413 mL HNO2; 587 mL KNO2

17. The following question refers to the following system: A 1.0-liter solution contains 0.25 M HF and 1.30 M NaF (Ka for HF is 7.2 × 10-4). If one adds 0.30 liters of 0.020 M KOH to the solution, what will be the change in pH?
0.73
-0.08
3.87
0.01
-0.19

18. Consider the titration of 300.0 mL of 1.400 M NH3 (Kb = 1.8 × 10-5) with 0.500 M HNO3. After 150.0 mL of 0.500 M HNO3 have been added, the pH of the solution is:
11.92
9.92
4.08
6.92
None of these choices are correct.

19. A 75.0-mL sample of 0.0500 M HCN (Ka = 6.2 × 10-10) is titrated with 0.420 M NaOH. What is the [H+] in the solution after 3.0 mL of 0.420 M NaOH have been added?
2.0 M
× 10-7 M
1.2 × 10-9 M
8.2 × 10-6 M
None of these choices are correct.

20. Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range. Which indicator would be best for the following titration?
0.100 M HF (Ka = 7.2 × 10-4) + 0.100 M NaOH
cresol red (7.0 - 8.8)
crystal violet (0.2 - 1.8)
phenolphthalien (8.2 - 10.0)
bromothymol blue (6.0 - 7.6)
erythosin B (2.2 - 3.5)

21. An aqueous solution contains 0.33 M nitrous acid. One Liter of this solution could be converted into a buffer by the addition of:
(Assume that the volume remains constant as each substance is added.)
0.166 mol KOH
0.34 mol NaNO2
0.17 mol HI
0.33 mol NaI
0.34 mol HI

Added by Carla A.

1. Which of the following aqueous solutions are good buffer systems? A. 0.14 M acetic acid + 0.13 M nitric acid. 0.13 M calcium hydroxide + 0.22 M calcium chloride. 0.39 M potassium nitrate + 0.23 M calcium nitrate. 0.24 M hydrochloric acid + 0.16 M potassium chloride. 0.27 M ammonia + 0.39 M ammonium nitrate. B.0.34 M calcium bromide + 0.29 M sodium bromide 0.24 M nitric acid + 0.16 M potassium nitrate 0.15 M potassium hydroxide + 0.24 M potassium bromide 0.10 M hydrocyanic acid + 0.20 M sodium cyanide 0.27 M ammonia + 0.40 M sodium hydroxide C. 0.10 M nitrous acid + 0.11 M sodium nitrite 0.27 M ammonium bromide + 0.36 M ammonia 0.25 M hydroiodic acid + 0.24 M sodium iodide 0.19 M sodium hydroxide + 0.29 M sodium chloride 0.40 M hypochlorous acid + 0.22 M potassium hypochlorite 2a. A solution contains 0.155 M sodium acetate and 0.496 M acetic acid. The pH of this solution is b. A solution contains 0.482 M sodium cyanide and 0.406 M hydrocyanic acid. The pH of this solution is c. A solution contains 0.400 M sodium nitrite and 0.225 M nitrous acid. The pH of this solution is 3a. A solution contains 0.496 M NH4I and 6.61×10-2 M ammonia. The pH of this solution is b. A solution contains 0.406 M NH4I and 0.187 M ammonia. The pH of this solution is c. The compound ethylamine is a weak base like ammonia. A solution contains 0.189 M C2H5NH3+ and 0.135 M ethylamine, C2H5NH2. The pH of this solution is 4a. A buffer solution is 0.498 M in CH3COOH and 0.247 M in CH3COONa. If Ka for CH3COOH is 1.8×10-5, what is the pH of this buffer solution? b. A buffer solution is 0.458 M in H2S and 0.392 M in KHS. If Ka1 for H2S is 1.0*10-7 , what is the pH of this buffer solution? c. A buffer solution is 0.312 M in NaHSO3 and 0.305 M in Na2SO3. If Ka for HSO3- is 6.4*10-8, what is the pH of this buffer solution? 5a. An aqueous solution contains 0.24 M ammonia. One liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) 0.25 mol HClO4 0.24 mol BaCl2 0.12 mol HClO4 0.12 mol KOH 0.25 mol NH4Cl b. An aqueous solution contains 0.26 M hydrofluoric acid. One Liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) 0.27 mol KF 0.131 mol NaOH 0.13 mol HBr 0.26 mol KCl 0.27 mol HBr c. An aqueous solution contains 0.30 M ammonium bromide. One liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) 0.30 mol HNO3 0.14 mol NaOH 0.29 mol NH3 0.14 mol HNO3 0.29 mol KBr 6a. A buffer solution made from CH3COOH and CH3COONa has a pH of 4.43. If pKa for CH3COOH is 4.74, what is the [CH3COO-]/[CH3COOH] in the buffer? b. The pKa value for H2CO3 is 6.38. What mole ratio of KHCO3 to H2CO3 is needed to prepare a buffer with a pH of 6.18? c. The pKa value for HCO3- is 10.30. What mole ratio of Na2CO3 to NaHCO3 is needed to prepare a buffer with a pH of 9.97. 7a. How many grams of solid sodium acetate should be added to 1.00 L of a 0.298 M acetic acid solution to prepare a buffer with a pH of 5.362 ? b. How many grams of solid sodium cyanide should be added to 1.50 L of a 0.248 M hydrocyanic acid solution to prepare a buffer with a pH of 8.418? c. How many grams of solid ammonium chloride should be added to 0.500L of a 0.147 M ammonia solution to prepare a buffer with a pH of 8.370 ? 8A. A 1 liter solution contains 0.538 M hydrocyanic acid and 0.404 M sodium cyanide. Addition of 0.202 moles of hydrochloric acid will: (Assume that the volume does not change upon the addition of hydrochloric acid.) Raise the pH slightly Lower the pH slightly Raise the pH by several units Lower the pH by several units Not change the pH Exceed the buffer capacity B. A 1 liter solution contains 0.313 M acetic acid and 0.417 M potassium acetate. Addition of 0.078 moles of barium hydroxide will: (Assume that the volume does not change upon the addition of barium hydroxide.) Raise the pH slightly Lower the pH slightly Raise the pH by several units Lower the pH by several units Not change the pH Exceed the buffer capacity C. A 1 liter solution contains 0.357 M hypochlorous acid and 0.268 M potassium hypochlorite. Addition of 0.295 moles of hydrobromic acid will: (Assume that the volume does not change upon the addition of hydrobromic acid.) Raise the pH slightly Lower the pH slightly Raise the pH by several units Lower the pH by several units Not change the pH Exceed the buffer capacity 9A. A buffer solution is made that is 0.368 M in HF and 0.368 M in NaF. If Ka for HF is 7.20*10-4 , what is the pH of the buffer solution? pH = ______ Write the net ionic equation for the reaction that occurs when 0.105 mol HNO3 is added to 1.00 L of the buffer solution. (Use the lowest possible coeffieicents, Omit state of matter. Use H3O+ instead of H+) B. A buffer solution is made that is 0.420 M in H2CO3 and 0.420 M in KHCO3. If Ka1 for H2CO3 is 4.20*10-7, what is the pH of the buffer solution? pH = ____ Write the net ionic equation for the reaction that occurs when 0.085 mol HCl is added to 1.00 L of the buffer solution. (Use the lowest possible coefficients. Omit states of matter. Use H3O+ instead of H+) C. A buffer solution is made that is 0.378 M in HNO2 and 0.378 M in NaNO2. If Ka for HNO2 is 4.50*10-4, what is the pH of the buffer solution? pH = Write the net ionic equation for the reaction that occurs when 0.085 mol KOH is added to 1.00 L of the buffer solution. (Use the lowest possible coefficients. Omit states of matter.) 10A. The pKa value for CH3COOH is 4.74. Would a buffer prepared from CH3COOH and CH3COONa with a pH of 4.24 be considered to be an effective buffer? _____ (Yes or No) A buffer in which the mole ratio of NaCH3COO to CH3COOH is 0.49 has a pH of 4.43. Would this buffer solution have a greater capacity for added acid (H3O+) or added base (OH-)? B. A buffer solution that is 0.458 M in HCN and 0.458 M in KCN has a pH of 9.40. The addition of 0.01 mol of OH- to 1.0 L of this buffer would cause the pH to _________ (increase slightly, increase by 2 units, decrease slightly, decrease by 2 units or not change) The capacity of this buffer for added OH- could be increased by the addition of 0.139 mol _________ (of the weak acid, or of the salt). C. A buffer solution that is 0.378 M in HNO2 and 0.378 M in NaNO2 has a pH of 3.35. Addition of which of the following would increase the capacity of the buffer for added OH-? (Select all that apply.) both HNO2 and NaNO2 HNO2 pure water NaNO2 none of the above 11A. A buffer solution contains 0.492 M KHSO3 and 0.372 M K2SO3. If 0.0479 moles of potassium hydroxide are added to 225 mL of this buffer, what is the pH of the resulting solution? (Assume that the volume does not change upon adding potassium hydroxide) B. A buffer solution contains 0.356 M NaHCO3 and 0.347 M Na2CO3. If 0.0608 moles of hydrobromic acid are added to 250. mL of this buffer, what is the pH of the resulting solution ? (Assume that the volume does not change upon adding hydrobromic acid) C. A buffer solution contains 0.292 M acetic acid and 0.443 M sodium acetate. If 0.0188 moles of nitric acid are added to 125 mL of this buffer, what is the pH of the resulting solution ? (Assume that the volume does not change upon adding nitric acid) 12A. A buffer solution contains 0.306 M NaH2PO4 and 0.299 M K2HPO4. Determine the pH change when 0.081 mol KOH is added to 1.00 L of the buffer. pH change = _____ B. A buffer solution contains 0.420 M KHSO3 and 0.256 M K2SO3. Determine the pH change when 0.052 mol HCl is added to 1.00 L of the buffer. pH change = ____ C. Determine the pH change when 0.080 mol HBr is added to 1.00 L of a buffer solution that is 0.378 M in HNO2 and 0.356 M in NO2-. pH change = ______

Adi S.

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