CHM1 18 End of Chapter Problems Collection

1. It has been calculated that a 0.150 M solution of formic acid at 25°C (pKa = 3.75) has a pH of 2.28. Is there a change to the pH of the solution if enough solid sodium formate is added to make the final formate concentration 0.100 M in 100 mL total (assume that the formic acid concentration does not change)?

2. 100 mL buffer solution contains 0.135 M HCO2H and 0.215 M HCO2Na and had a pH of 3.95.

a) What is the final pH if 5.00 mL of 1.00 M HCl are added to 100 mL of this solution?

b) What is the final pH if 5.00 mL of 1.00 M NaOH are added?

3.100 mL of a buffer solution contains 0.119 M pyridine and 0.234 M pyridine hydrochloride and had a pH of 4.94.

What is the final pH if 12.0 mL of 1.5 M NaOH are added to 250 mL of this solution?

What is the final pH if 12.0 mL of 1.5 M HCl are added?

4. What is the pH of a solution which is 0.0400 M in formic acid, HCO2H, and 0.0600 M in sodium formate, NaHCOO?

(a) 3.92            (b) 3.96            (c) 4.00            (d) 9.52           (e) 4.08

5.What is the pH of a solution containing aqueous ammonia and ammonium nitrate in a

molar ratio of 5.0 to 3.0?

(a) 4.52            (b) 4.96            (c) 9.04            (d) 9.26           (e) 9.48

6. Determine the pH at each of the following points in the titration of 15 mL of 0.1 M HI with 0.5 M LiOH

1. When no LiOH is added
2. When 2 mL LiOH added
3. When 3 mL LiOH added
4. When 4 mL LiOH added

7. Determine the pH at each of the following points in the titration of 10 mL of 0.05 M Ba(OH)₂ with 0.1 M HNO₃

1. When no HNO₃ is added
2. When 5 mL HNO₃ added
3. When 10 mL HNO₃ added
4. When 15 mL HNO₃ added

8. When does the equivalence point of 15 mL of 0.15 M CH₃COOH titrated with 0.1 M NaOH occur?

9. Sketch a titration curve for the titration of 25.0 mL of 0.125 M NH₃ with 0.0625 M HCl given the following data points:

V_HCl = 5 mL, pH = 10.24 

V_HCl = 45 mL, pH = 8.24

V_HCl = 60 mL, pH = 2.13 

V_HCl = 80 mL, pH = 1.75 

10. Blood is buffered by carbonic acid and the bicarbonate ion. Normal blood plasma is 0.024 M in HCO₃^- and 0.0012 M H₂CO₃ (pk_a for H₂CO₃at body temperature is 6.1).

a) What is the pH of blood plasma?
b) If the volume of blood in a normal adult is 5.0L, what mass of HCl could be neutralized by the buffering system in blood before the pH falls below 7.0 (which would result in death)?
c) Given the volume from part (b), what mass of NaOH could be neutralized before the pH rises above 7.8?

11. Which buffer system is the best choice to create a buffer with pH = 9.007? For the best system, calculate the ratio of the masses of the buffer components required to make the buffer.
HF/KF
HNO₂/KNO₂
NH₃/NH₄Cl
HClO/KClO

12. A 30.0 mL sample of 0.165 M propanoic acid is titrated with 0.300 M KOH. Calculate the pH at each volume of added base: 0 mL, 5 mL, 10 mL, equivalence point, one-half equivalence point, 20 mL, 25 mL. Use your calculations to make a sketch of the titration curve.

13.What is the pH of a solution that contains

1. 0.333 M benzoic acid and 0.252 M sodium benzoate?
2. 0.050 M trimethylamine and 0.066 M trimethylamine hydrochloride?

The pK_a of benzoic acid is 4.20, and the pK_b of trimethylamine is also 4.20.

14.The buffer solution from Example 15 contained 0.119 M pyridine and 0.234 M pyridine hydrochloride and had a pH of 4.94.

1. What is the final pH if 12.0 mL of 1.5 M NaOH are added to 250 mL of this solution?
2. What is the final pH if 12.0 mL of 1.5 M HCl are added?

15.Salicylic acid is used in the synthesis of acetylsalicylic acid, or aspirin. One gram dissolves in 460 mL of water to create a saturated solution with a pH of 2.40.

1. What is the K_a of salicylic acid?
2. What is the final pH of a saturated solution that is also 0.238 M in sodium salicylate?
3. What is the final pH if 10.00 mL of 0.100 M HCl are added to 150.0 mL of the buffered solution?
4. What is the final pH if 10.00 mL of 0.100 M NaOH are added to 150.0 mL of the buffered solution?

16. Calculate the pH of a solution prepared by adding 40.00 mL of 0.237 M HCl to 75.00 mL of a 0.133 M solution of NaOH.

17. Calculate the pH of a solution prepared by adding 45.0 mL of a 0.213 M HCl solution to 125.0 mL of a 0.150 M solution of ammonia. The pK_b of ammonia is 4.75 at 25°C.

18. What volume of 0.50 M HCl is needed to completely neutralize 25.00 mL of 0.86 M NaOH?

19. 

Fill in the data for the titration of 50.0 mL of 0.241 M formic acid with 0.0982 M KOH. The pK_a of formic acid is 3.75. What is the pH of the solution at the equivalence point?

Volume of Base Added (mL)	0	5	10	15	20	25
pH

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