Chapter 15 4 What is the pH of a solution prepared by dissolving

35) What is the pH of a solution prepared by dissolving 0.30 grams of solid CaO (lime) in enough water to

make 2.00 L of aqueous Ca(OH)2 (limewater)?

CaO(s) + H2O(l) → Ca2+(aq) + 2 OH–(aq)

A) 2.27

B) 2.57

C) 11.42

D) 11.73

36) What is the pH of a solution prepared by diluting 75.00 mL of 0.10 M HCl with enough water to

produce a total volume of 100.00 mL?

A) 1.00

B) 1.12

C) 2.00

D) 2.24

37) What is the pH of a solution prepared by diluting 50.00 mL of 0.020 M Ba(OH)2 with enough water to

produce a total volume of 250.00 mL?

A) 2.10

B) 2.40

C) 11.60

D) 11.90

38) What is the pH of a solution prepared by mixing 100.00 mL of 0.20 M HCl with 50.00 mL of 0.30 M

HCl? Assume that the volumes are additive.

A) 0.25

B) 0.30

C) 0.63

D) 1.70

39) What is the pH of a solution prepared by mixing 100.00 mL of 0.020 M Ca(OH)2 with 50.00 mL of

0.200 M NaOH? Assume that the volumes are additive.

A) 12.90

B) 12.97

C) 13.15

D) 13.45

40) What is the pH of a 0.020 M RbOH solution?

A) 0.020

B) 0.040

C) 1.70

D) 12.30

41) What is the pH of a solution prepared by mixing 100.00 mL of 0.025 M Ca(OH)2 with 50.00 mL of

0.080 M LiOH? Assume that the volumes are additive.

A) 12.67

B) 12.78

C) 12.95

D) 13.25

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42) What is the hydronium ion concentration of a 0.300 M acetic acid solution with Ka = 1.8 × 10-5? The

equation for the dissociation of acetic acid is:

CH3CO2H(aq) + H2O(l) ⇌ H3O+(aq) + CH3CO2–(aq).

A) 2.3 × 10-2 M

B) 4.2 × 10-2 M

C) 2.3 × 10–3 M

D) 4.2 × 10-3 M

43) What is the hydronium ion concentration of a 0.200 M hypochlorous acid solution with

The equation for the dissociation of hypochlorous acid is:

HOCl(aq) + H2O(l) ⇌ H3O+(aq) + OCl–(aq).

A) 1.9 × 10–4 M

B) 8.4 × 10–4 M

C) 3.7 × 10–5 M

D) 8.4 × 10–5 M

44) Potassium hydrogen phthalate (molar mass = 204.2 g/mol)is one of the most commonly used acids for

standardizing solutions containing bases. KHP is a monoprotic weak acid with Calculate

the pH of the solution that results when 0.40 g of KHP is dissolved in enough water to produce 25.0 mL

of solution.

A) 2.10

B) 3.26

C) 4.30

D) 5.41

45) A 0.50 M solution of a weak acid HA has the same pH as a 0.075 M solution of HCl. Calculate the Ka

for HA.

A) 0.50

B) 0.075

C) 0.1324

D) 0.01125

46) A weak base ionizes in water as follows:

B(aq) + H2O(l) ⇌ BH+(aq) + OH–(aq)

A 0.150 M solution of B is 2.500 % ionized at 25ºC. What is the pH of this solution?

A) 0.40

B) 2.43

C) 11.57

D) 13.60

47) Calculate the pH of a 0.060 M carbonic acid solution, H2CO3(aq), that has the stepwise dissociation

constants Ka1 = 4.3 × 10-7 and Ka2 = 5.6 × 10–11.

A) 1.22

B) 3.79

C) 6.37

D) 10.25

48) Calculate the pH of a 0.20 M H2SO3, solution that has the stepwise dissociation constants Ka1 = 1.5 ×

10-2 and Ka2 = 6.3 × 10-8.

A) 1.26

B) 1.32

C) 1.82

D) 2.52

49) Calculate the concentration of bicarbonate ion, HCO3–, in a 0.050 M H2CO3 solution that has the

stepwise dissociation constants Ka1 = 4.3 × 10-7 and Ka2 = 5.6 × 10–11.

A) 1.5 × 10-4 M

B) 4.3 × 10-7 M

C) 2.2 × 10–8 M

D) 5.6 × 10–11 M

50) What is the pH of a 0.20 M H2Se solution that has the stepwise dissociation constants Ka1 = 1.3 × 10–4

and Ka2 = 1.0 × 10–11?

A) 2.29

B) 3.89

C) 4.59

D) 5.57

51) What is the selenide ion concentration [Se2-] for a 0.400 M H2Se solution that has the stepwise

dissociation constants of Ka1 = 1.3 × 10–4 and Ka2 = 1.0 × 10–11?

A) 7.2 × 10-3 M

B) 1.3 × 10-4 M

C) 5.2 × 10–5 M

D) 1.0 × 10–11 M

52) Which of the following is a weak diprotic acids?

A) HCN

B) H CO2H

C) H2CO3

D) H2SO3

53) What is the pH of a 0.300 M NH3 solution that has Kb = 1.8 × 10-5? The equation for the dissociation of

NH3 is

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH–(aq).

A) 2.11

B) 2.63

C) 11.89

D) 11.37

54) What is the pH of a 2.4 M pyridine solution that has Kb = 1.9 × 10-9? The equation for the dissociation

of pyridine is

C5H5N(aq) + H2O(l) ⇌ C5H5NH+(aq) + OH–(aq).

A) 4.17

B) 8.72

C) 9.83

D) 10.83

55) Aniline, (C6H5NH2, Kb = 4.3 × 10–10 at 25°C) is an industrially important amine used in the making of

dyes. Determine the pH of an aniline solution made by dissolving 3.90 g of aniline in enough water to

make 100 mL of solution.

A) 4.87

B) 9.13

C) 9.74

D) 10.74

56) Determine the ammonia concentration of an aqueous solution that has a pH of 11.30. The equation for

the dissociation of NH3 (Kb = 1.8 × 10-5) is

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH–(aq).

A) 2.7 M

B) 0.22 M

C) 9.0 × 10–3 M

D) 2.0 × 10-3 M

57) What is the relationship between Ka and Kb at 25°C for a conjugate acid base pair?

A) Ka × Kb = 1 × 10–14

B) Ka/Kb = 1 × 10–14

C) Kb/Ka = 1 × 10–14

D) Ka – Kb = 1 × 10–14

58) Which one of the following salts, when dissolved in water, produces the solution with the highest

pH?

A) KHSO4

B) RbClO4

C) BaO

D) CH3CH3NH3Br

59) If an equal number of moles of the weak acid HF and the strong base KOH are added to water, is the

resulting solution acidic, basic, or neutral?

A) acidic

B) basic

C) neutral

D) There is insufficient information provided to answer this question.

60) Which one of the following salts, when dissolved in water, produces the solution with the highest

pH?

A) NaI

B) KBr

C) RbCl

D) CsF

61) Which one of the following salts, when dissolved in water, produces the solution with a pH closest to

7.00?

A) NH4I

B) Na2O

C) KHCO3

D) CsCl

62) Calculate the pH of a 0.200 M NaCH3CO2 solution. Ka for acetic acid, CH3CO2H, is 1.8 × 10-5.

A) 2.72

B) 4.98

C) 9.02

D) 11.28

63) Calculate the pH of a 0.800 M KBrO solution. Ka for hypobromous acid, HBrO, is 2.0 × 10-9.

A) 2.70

B) 4.40

C) 9.60

D) 11.30

64) Calculate the pH of a 0.100 M CH3NH3Cl solution. Kb for methylamine, CH3NH2, is 3.7 × 10–4.

A) 2.22

B) 5.78

C) 8.22

D) 11.78

65) Which one of the following salts, when dissolved in water, produces the solution with the lowest pH?

A) NaI

B) KI

C) MgI2

D) AlI3

66) Which of the following salts are acidic?

A) LiCl, NaCl, KCl

B) NH4Cl, CuCl2, AlCl3

C) NaCH3CO2, LiCH3CO2, RbCH3CO2

D) KCl, NH4Cl, Na2CO3

67) Which one of the following salts, when dissolved in water, produces the solution with the highest

pH?

A) LiHSO4

B) NaClO4

C) KF

D) CH3NH3I

68) Which one of the following salts, when dissolved in water, produces the solution with the highest

pH?

A) LiI

B) LiBr

C) LiCl

D) LiF

69) Which one of the following salts, when dissolved in water, produces the solution with the lowest pH?

A) RbCl

B) NH4Cl

C) SrCl2

D) AlCl3

70) Which one of the following is not considered to be a Lewis base?

A) H2S

B) NH3

C) NH4+

D) Cl–

71) Which one of the following is least able to behave as a Lewis base?

A) CH3NH2

B) (CH3)2NH

C) (CH3)3N

D) (CH3)2NCH2CH3+

72) The compound BCl3 can be described as a(n)

A) Arrhenius acid.

B) Br∅nsted-Lowry base.

C) Lewis acid.

D) Lewis base.

73) Identify the set of Lewis acids.

A) BH3, BF3, Cu2+, CO2

B) Cl–, OH–, NBr3, H2O

C) H3PO4, H2PO4–, HPO42-, PO43-

D) CCl3–, NH2–, CN–, F–

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15.3 Short Answer Questions

1) The Br∅nsted-Lowry acids in the chemical equation below are ________ and ________.

HNO2(aq) + H2O(l) ⇌ H3O+(aq) + NO2–(aq)

2) The equilibrium constant for the reaction below has the value Ka = 3.5 × 10-4. In this reaction the

stronger Br∅nsted-Lowry acid is ________ and the weaker Br∅nsted-Lowry acid is ________.

HF(aq) + H2O(l) ⇌ H3O+(aq) + F–(aq)

3) A proton hydrated by ten water molecules has the formula ________.

4) The number of waters of hydration in the hydrate proton H11O5+ is ________.

5) A solution with hydronium ion concentration [H+] = 1.60 × 10-2 M has a hydroxide ion concentration

[OH–] = ________.

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6) The concentration of H3O+ in human sweat can be as low as 2.5 × 10-6. The concentration of OH– in the

sweat is ________, and this solution is ________ (acidic, basic, neutral).

7) Undersea flora prefer a maximum concentration of OH– of 1.58 × 10-5. The concentration of H3O+ in

the seawater is ________, and this solution is ________ (acidic, basic, neutral).

8) At the normal body temperature of 37°C, Kw = 2.42 × 10–14. The H3O+ concentration of normal blood

ranges from 3.5 × 10-8 to 4.5 × 10–8. The OH– concentration of normal blood ranges from ________ to

________, and blood is ________ (acidic, basic, neutral).

9) At 50°C the value of Kw is 5.5 × 10–14, and the pH of a neutral solution at 50°C is ________.

10) One way to prepare a solution with a pH of 10.00 is to dissolve ________ grams of CaO in enough

water to make 500 mL of solution.

11) Bromothymol blue indicator changes color from yellow at a pH of 6.0 to blue at a pH of 7.6. Phenol

red indicator changes color from yellow at a pH of 6.8 to red at a pH of 8.4. A sample of pancreatic fluid

having [OH–] = 1.258 × 10-6 would impart a ________ color to bromothymol blue and a ________ color to

phenol red.

12) Bromothymol blue indicator changes color from yellow at a pH of 6.0 to blue at a pH of 7.6. Methyl

70

red indicator changes color from red at a pH of 4.4 to yellow at a pH of 6.2. A sample of saliva having

[H3O+] = 6.310 × 10-7 would impart a ________ color to bromothymol blue and a ________ color to methyl

red.

13) The pH of a 0.055 M KOH solution is ________.

14) The value of Ka for a 0.250 M HCN solution having a pH of 4.956 is ________.

15) In order for the reaction HA + HSO3– ⇌ A– + H2SO3 to have an equilibrium constant Kc < 1, the Ka of

HA must be ________ (greater, less) than the Ka of HSO3–.

16) In order for the reaction A– + H2CO3 ⇌ HA + HCO3– to have an equilibrium constant Kc < 1, the Ka of

HA must be ________ (greater, less) than the Ka of H2CO3.

17) A 1.25 × 10-4 M solution of the anti-inflammatory drug naproxen has a pH = 4.2. The Ka and pKa of

naproxen are ________ and ________.

18) Phenobarbital is an antiepileptic drug with a water solubility of 4.3 × 10–3 M and pKa = 7.4. What is

the pH and percent ionization of 4.3 × 10-3 M phenobarbital?

19) Phenobarbital has a pKa = 7.4. Compared to a 1.0 × 10-3 M solution, 1.0 × 10-4 M phenobarbital will

have a ________ (higher, lower) pH and a ________ (higher, lower) percent ionization.

20) Erythromycin is a basic antimicrobial with pKb = 5.2. A 1.0 × 10-3 M solution of erythromycin has a

pH of ________ and a ________ percent ionization.

21) A 0.050 M solution of hydroxylamine, NH2OH, having Kb = 9.1 × 10-9 has a pH of ________.

22) A 0.50 M KNO2 solution will have a pH ________ seven.

23) The acid strength of an oxoacid having the general formula HnYOm increases as the electronegativity

of Y ________ and as the oxidation number of Y ________.

24) In the aquation reaction Co2+ + 6 H2O → [Co(H2O)6]2+, the Lewis acid is ________ and the Lewis

base is ________.

25) In the reaction between NO2 and H2O that produces HNO3, the Lewis acid is ________ and the Lewis

base is ________.