University of South Florida

COURSE TITLE: CHM 2046

1)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 Ka of hydrazoic acid is 1.9 × 10-5.

1. 1. 1. H2O
      2. H3O+
      3. azide
      4. hydrazoic acid
      5. This is a buffer solution: the pH does not change upon addition of acid or base.

 

1. 2. A solution is prepared by dissolving 0.23 mol of nitrous acid and 0.27 mol of sodium nitrite 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 Ka of nitrous acid is 1.36 × 10-3.
      1. H2O
      2. H3O+
      3. nitrite ion
      4. nitrous acid
      5. This is a buffer solution: the pH does not change at all upon addition of acid or base.

 

1. 3. Calculate the pH of a solution that is 0.295 mol L-1 in sodium formate (HCOONa) and 0.205 mol L-1 in formic acid (HCOOH). The Ka of formic acid is 1.77 × 10-4.

A) 3.910

B) 3.587

C) 13.84

D) 10.10

E) 4.963

 

1. 4. Calculate the pH of a solution that is 0.210 mol L-1 in nitrous acid (HNO2) and 0.290 mol L-1 in potassium nitrite (KNO2). 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

 

1. 5. Calculate the percent ionization of nitrous acid in a solution that is 0.210 mol L-1 in nitrous acid (HNO2) and 0.290 mol L-1 in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.50 × 10-4.

A) 58.0

B) 0.154

C) 16.6

D) 2.74 × 10-3

E) 1.55

 

1. 6. Calculate the percent ionization of nitrous acid in a solution that is 0.249 mol L-1 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

 

1. 7. What is the pH of a buffer solution that is 0.211 mol L-1 in lactic acid and 0.111 mol L-1 in sodium lactate? The Ka of lactic acid is 1.4 × 10-4.

A) 14.28

B) 10.43

C) 5.48

D) 3.57

E) 4.13

 

1. 8. What is the pH of a buffer solution that is 0.255 mol L-1 in hypochlorous acid (HClO) and

0.333 mol L-1 in sodium hypochlorite (NaClO)? The Ka of hypochlorous acid is 3.8 × 10-8. A) 13.88

B) 6.46

C) 8.49

D) 7.30

E) 7.54

1. 9. What is the pH of a solution prepared by mixing 25.00 mL of 0.10 mol L-1 CH3COOH with

25.00 mL of 0.010 mol L-1 CH3COONa? Assume that the volume of the solutions are additive and that Ka = 1.8 × 10-5 for CH3COOH.

A) 2.87

B) 3.74

C) 4.75

D) 5.74

 

1. 10. What is the pH of a solution prepared by mixing 50.00 mL of 0.10 mol L-1 NH3 with 5.00 mL of 0.10 mol L-1 NH4Cl? Assume that the volume of the solutions are additive and that Kb = 1.8 × 10-5 for NH3.

A) 8.25

B) 9.28

C) 10.26

D) 11.13

 

1. 11. What is the pH of a solution prepared by mixing 50.00 mL of 0.10 mol L-1 methylamine, CH3NH2, with 20.00 mL of 0.10 mol L-1 methylammonium chloride, CH3NH3Cl? Assume that the volume of the solutions are additive and that Kb = 3.70 × 10-4 for methylamine.

A) 10.17

B) 10.57

C) 10.97

D) 11.78

1. 12. What is the pH of a buffer system prepared by dissolving 10.70 grams of NH4Cl and 25.00 mL of 12 mol L-1 NH3 in enough water to make 1.000 L of solution? Kb = 1.80 × 10-5 for NH3. A) 9.08

B) 9.26

C) 9.43

D) 11.32

 

1. 13. What is the pH of a solution prepared by mixing 100.00 mL of 0.020 mol L-1 Ca(OH)2 with

50.00 mL of 0.300 mol L-1 NaOH? Assume that the volumes are additive. A) 13.05

B) 13.10

C) 13.28

D) 13.58

 

1. 14. What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 mol L-1 HCN with 50.00 mL of 0.030 mol L-1 NaCN? Assume that the volumes of the solutions are additive and that Ka = 4.9 × 10-10 for HCN.

A) 1.5 × 10-10 mol L-1

B) 4.9 × 10-10 mol L-1

C) 1.6 × 10-9 mol L-1

D) 7.0 × 10-6 mol L-1

1. 15. What is the [CH3COO-]/[CH3COOH] ratio necessary to make a buffer solution with a pH of 4.34?

Ka = 1.8 × 10-5 for CH3COOH.

A) 0.39:1

B) 0.91:1

C) 1.09:1

D) 2.5:1

 

1. 16. What volume of 5.00 × 10-3 mol L-1 HNO3 is needed to titrate 80.00 mL of 5.00 × 10-3 mol L-1 Ca(OH)2 to the equivalence point?
       1. 10.0 mL
       2. 40.0 mL
       3. 80.0 mL
       4. 160. mL

 

1. 17. What is the pH of a solution made by mixing 25.00 mL of 0.100 mol L-1 HCl with 40.00 mL of 0.100 mol L-1 KOH? Assume that the volumes of the solutions are additive.

A) 0.64

B) 1.64

C) 12.36

D) 13.36

 

 

 

 

1. 18. How many millilitres of 0.0850 mol L-1 NaOH are required to titrate 25.0 mL of 0.0720 mol L-1 HBr to the equivalence point?

A) 21.2

B) 0.245

C) 3.92

D) 0.153

E) 29.5

 

1. 19. How many millilitres of 0.120 mol L-1 NaOH are required to titrate 50.0 mL of 0.0998 mol L-1 butanoic acid to the equivalence point? Butanoic acid is monoprotic. The Ka of butanoic acid is 1.5 × 10-5.

A) 4.90

B) 50.0

C) 41.6

D) 60.1

E) 4.65

 

1. 20. A 25.0 mL sample of 0.150 mol L-1 hydrofluoric acid is titrated with a 0.150 mol L-1 NaOH solution. What is the pH at the equivalence point? The Ka of hydrofluoric acid is 3.5 × 10-4.

A) 10.17

B) 10.83

C) 3.17

D) 7.00

E) 8.17

 

1. 21. A 25.0 mL sample of 0.150 mol L-1 butanoic acid is titrated with a 0.150 mol L-1 NaOH solution. What is the pH before any base is added? Butanoic acid is monoprotic. The Ka of butanoic acid is 1.5 × 10-5.

A) 2.83

B) 1.5 × 10-3

C) 4.82

D) 4.00

E) 1.0 × 104

1. 22. A 25.0 mL sample of 0.150 mol L-1 hypochlorous acid is titrated with a 0.150 mol L-1 NaOH solution. What is the pH after 26.0 mL of base is added? The Ka of hypochlorous acid is 3.0 × 10-8.

A) 2.54

B) 11.47

C) 7.00

D) 7.51

E) 7.54

 

1. 23. 

       What is the approximate pH at the equivalence point of a weak acid-strong base titration if 25 mL of aqueous formic acid (HCOOH) requires 29.80 mL of 0.3567 mol L-1 NaOH? Ka =1.8

× 10-4 for formic acid. A) 2.06

B) 5.48

C) 8.52

D) 11.94

 

1. 24. What is the approximate pH at the equivalence point of a weak acid-strong base titration if

25 mL of aqueous hydrofluoric acid requires 30.00 mL of 0.400 mol L-1 NaOH? Ka = 6.76 × 10- 4 for HF.

A) 1.74

B) 5.75

C) 8.25

D) 12.26

 

1. 25. Formic acid (HCOOH, Ka = 1.8 × 10-4) is the principal component in the venom of stinging ants. What is the molarity of a formic acid solution if 25.00 mL of the formic acid solution requires 29.80 mL of 0.0567 mol L-1 NaOH to reach the equivalence point?

A) 0.0134 mol L-1

B) 0.0476 mol L-1

C) 0.0567 mol L-1

D) 0.0676 mol L-1

 

 

 

 

1. 26. Sodium hypochlorite, NaOCl, is the active ingredient in household bleach. What is the concentration of hypochlorite ion if 20.00 mL of bleach requires 32.00 mL of 0.500 mol L-1 HCl to reach the equivalence point?

A) 0.300 mol L-1

B) 0.312 mol L-1

C) 0.800 mol L-1

D) 1.30 mol L-1

 

 

1. 27. What is the pH of the resulting solution if 25.00 mL of 0.10 mol L-1 acetic acid is added to

10.00 mL of 0.10 mol L-1 NaOH? Assume that the volumes of the solutions are additive. Ka =

1.8 × 10-5 for CH3COOH.

A) 9.43

B) 9.08

C) 4.92

D) 4.57

 

1. 28. What is the pH of a solution made by mixing 10.00 mL of 0.10 mol L-1 acetic acid with

10.00 mL of 0.10 mol L-1 KOH? Assume that the volumes of the solutions are additive. Ka = 1.8

× 10-5 for CH3COOH. A) 5.28

B) 7.00

C) 8.72

D) 10.02

 

1. 29. What is the pH of a solution made by mixing 30.00 mL of 0.10 mol L-1 acetic acid (CH3COOH) with 50.00 mL of 0.100 mol L-1 KOH? Assume that the volumes of the solutions are additive. Ka = 1.8 × 10-5 for CH3COOH.

A) 8.26

B) 9.26

C) 11.13

D) 12.40

1. 30. What is the pH at the equivalence point of a weak base-strong acid titration if 20.00 mL of NaOCl requires 28.30 mL of 0.50 mol L-1 HCl for complete neutralization? Ka = 3.0 × 10-8 for HOCl.

A) 0.30

B) 3.18

C) 3.76

D) 4.03

 

1. 31. What is the pH of the resulting solution if 45 mL of 0.432 mol L-1 methylamine, CH3NH2, is added to 15 mL of 0.234 mol L-1 HCl? Assume that the volumes of the solutions are additive. Ka = 2.70 × 10-11 for CH3NH3+.

A) 2.77

B) 4.09

C) 9.91

D) 11.23

 

1. 32. A 25.0 mL sample of 0.150 mol L-1 hydrazoic acid is titrated with a 0.150 mol L-1 NaOH solution. What is the pH after 13.3 mL of base is added? The Ka of hydrazoic acid is 1.9 × 10-5. A) 4.45

B) 1.34

C) 3.03

D) 4.78

E) 4.66

 

1. 33. Calculate the solubility (in g L-1) of calcium fluoride in water at 25 °C if the Ksp for CaF2 is 1.5 × 10-10.

A) 9.6 × 10-4 g L-1

B) 2.6 × 10-2 g L-1

C) 3.3 × 10-2 g L-1

D) 4.1 × 10-2 g L-1

1. 34. Calculate the Ksp for silver sulfite if the solubility of Ag2SO3 in pure water is 4.6 × 10-3 g L-1.

A) 3.8 × 10-15

B) 1.5 × 10-14

C) 2.4 × 10-10

D) 4.8 × 10-10

1. 35. What is the molar solubility of Mg(OH)2 in a basic solution with a pH of 12.50? Ksp for Mg(OH)2 is 5.6 × 10-12.

A) 1.8 × 10-10 mol L-1

B) 5.6 × 10-9 mol L-1

C) 2.4 × 10-6 mol L-1

D) 1.1 × 10-4 mol L-1

1. 36. Calculate the molar solubility of thallium chloride (TlCl) in 0.40 mol L-1 NaCl at 25 °C. Ksp for TlCl is 1.7 × 10-4.

A) 6.8 × 10-5 mol L-1

B) 4.2 × 10-4 mol L-1

C) 8.2 × 10-3 mol L-1

D) 1.3 × 10-2 mol L-1

1. 37. In which of the following solutions would solid PbBr2 be expected to be the least soluble at 25 °C?
       1. 0.1 mol L-1 HBr
       2. 0.1 mol L-1 NaBr
       3. 0.1 mol L-1 CaBr2
       4. 0.1 mol L-1 K NO3
   38. What is the molar solubility of silver chloride (AgCl) in water? The solubility-product constant for AgCl is 1.8 × 10-10 at 25 °C.

A) 9.0 × 10-11 mol L-1

B) 3.6 × 10-10 mol L-1

C) 9.74 mol L-1

D) 1.9 × 10-5 mol L-1

E) 1.3 × 10-5 mol L-1

1. 39. What is the molar solubility of barium fluoride (BaF2) in water? The solubility-product constant for BaF2 is 1.7 × 10-6 at 25 °C.

A) 6.5 × 10-4 mol L-1

B) 1.2 × 10-2 mol L-1

C) 1.8 × 10-3 mol L-1

D) 7.5 × 10-3 mol L-1

E) 5.7 × 10-7 mol L-1

1. 40. What is the molar solubility of AgCl in 0.40 mol L-1 NH3? Ksp for AgCl is 1.8 × 10-10 and

Kf for Ag(NH3)2+ is 1.7 × 107. A) 1.3 × 10-5 mol L-1

B) 2.0 × 10-5 mol L-1

C) 2.2 × 10-2 mol L-1

D) 5.5 × 10-2 mol L-1

1. 41. What is the molar solubility of AgCl in 0.10 mol L-1 NaCN if the colourless complex ion Ag(CN)2- forms? Ksp for AgCl is 1.8 × 10-10 and Kf for Ag(CN)2- is 1.0 × 1021.

A) 0.050 mol L-1

2. 0.10 mol L-1
3. 0.20 mol L-1
4. 0.40 mol L-1

 

1. 42. Solid potassium chromate (K2CrO4) is slowly added to a solution containing 0.50 mol L-1 AgNO3 and 0.50 mol L-1 Ba(NO3)2. What is the Ag+ concentration when BaCrO4 just starts to precipitate? The Ksp for Ag2CrO4 and BaCrO4 are 1.1 × 10-12 and 1.2 × 10-10, respectively. A) 6.5 × 10-5 mol L-1

B) 1.3 × 10-4 mol L-1

C) 3.2 × 10-4 mol L-1

D) 6.8 × 10-2 mol L-1