Chapter 14 2 The percent dissociation of acetic acid changes as the concentration

74) Benzoic acid (C6H5CO2H = HBz) solutions are sometimes used in experiments to determine

the molarity of a basic solution of unknown concentration. What is the pH of a 0.100 M solution

of benzoic acid if and the equilibrium equation of interest is

A) 1.00

B) 2.59

C) 4.19

D) 5.19

75) 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

76) Vinegar is a 5.0% solution by weight of acetic acid (CH3CO2H) in water. Given that

for acetic acid and assuming the density of vinegar to be 1.00 g/cm3, what is the

pH of this vinegar solution?

A) 2.00

B) 2.41

C) 2.87

D) 4.74

77) Vinegar is a 5.0% solution by weight of acetic acid (CH3CO2H) in water. Given that the pH

for acetic acid is 2.41, the and assuming the density of vinegar to be 1.00 g/cm3,

what is the percent dissociation of acetic acid in vinegar?

A) 0.47%

B) 1.5%

C) 4.0%

D) 5.0%

78) What is the percent dissociation of a benzoic acid solution with pH = 2.59? The acid

dissociation constant for this monoprotic acid is

A) 0.50%

B) 1.5%

C) 2.5%

D) 3.5%

79) The percent dissociation of acetic acid changes as the concentration of the acid decreases. A

100-fold decrease in acetic acid concentration results in a ________ fold ________ in the percent

dissociation.

A) 10, increase

B) 10, decrease

C) 100, increase

D) 100, decrease

80) Which of the following are weak diprotic acids?

A) carbonic acid – H2CO3, hydrosulfuric acid – H2S, acetic acid – CH3CO2H

B) formic acid – HCO2H, acetic acid CH3CO2H, benzoic acid C6H5CO2H

C) carbonic acid – H2CO3, oxalic acid – H2C2O4, sulfurous acid – H2SO3

D) hydrocyanic acid – HCN, sulfuric acid – H2SO4, phosphoric acid – H3PO4

81) What is the second stepwise equilibrium constant expression for phosphoric acid H3PO4?

A) Ka2 = ([H3O+][H2PO4–])/([H3PO4])

B) Ka2 = ([H3O+]2[HPO42-])/([H3PO4])

C) Ka2 = ([H3O+]3[PO43-])/([H3PO4])

D) Ka2 = ([H3O+][HPO42-])/([H2PO4–])

82) Calculate the pH of a 0.020 M carbonic acid solution, H2CO3(aq), that has the stepwise

dissociation constants and

A) 1.70

B) 4.03

C) 6.37

D) 10.25

83) 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

84) Calculate the concentration of bicarbonate ion, HCO3–, in a 0.010 M H2CO3 solution that

has the stepwise dissociation constants and

A) 6.6 × 10-5 M

B) 4.3 × 10-7 M

C) 4.3 × 10-9 M

D) 5.6 × 10-11 M

85) What is the pH of a 0.10 M H2Se solution that has the stepwise dissociation constants Ka1 =

1.3 × 10-4 and Ka2 = 1.0 × 10-11?

A) 2.44

B) 3.89

C) 4.89

D) 5.50

86) What is the selenide ion concentration [Se2-] for a 0.100 M H2Se solution that has the

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

A) 3.6 × 10-3 M

B) 1.3 × 10-4 M

C) 1.3 × 10-5 M

D) 1.0 × 10-11 M

87) Which of the following can be classified as a weak base?

A) CH3NH2

B) NH2OH

C) Both CH3NH2 and NH2OH

D) Neither CH3NH2 nor NH2OH

88) What is the pH of a 0.100 M NH3 solution that has Kb = 1.8 × 10-5 ? The equation for the

dissociation of NH3 is

A) 1.87

B) 2.87

C) 11.13

D) 12.13

25

89) What is the concentration of N in a 0.20 M ammonia solution? The base dissociaton

constant for ammonia is 1.8 × .

A) 0.0019 M

B) 0.20 M

C) 0.020 M

D) 0.040 M

90) The concentration of C N in a 0.20 M methylamine (C ) solution is 2.32 ×

M. What is for methylamine?

A) 2.7 ×

B) 5.4 ×

C) 1.2 ×

D) 3.3 ×

91) What is the pH of a 0.30 M pyridine solution that has a Kb = 1.9 × 10-9 ? The equation for

the dissociation of pyridine is

A) 4.62

B) 8.72

C) 9.38

D) 10.38

92) 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

93) Determine the ammonia concentration of an aqueous solution that has a pH of 11.50. The

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

A) 2.5 M

B) 0.55 M

C) 5.7 × 10-3 M

D) 3.2 × 10-3 M

94) How many grams of pyridine are there in 100 mL of an aqueous solution that has a pH of

9.00? The Kb for pyridine is 1.9 × and the equation of interest is

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

A) 0.053 g

B) 0.42 g

C) 0.79 g

D) 7.9 g

95) 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

96) Ammonia NH3, has a base dissociation constant of 1.8 × 10-5. What is the conjugate acid of

ammonia and what is its acid dissociation constant?

A) NH4+, 1.9 × 109

B) NH4+, 1.8 × 10-5

C) NH4+, 5.6 × 10-10

D) NH2–, 5.6 × 10-10

97) Methylamine CH3NH2, has a base dissociation constant of 3.7 × 10-4. What is the conjugate

acid of methylamine and what is its acid dissociation constant?

A) CH3NH3+, 2.7 × 103

B) CH3NH3+, 3.7 × 10-4

C) CH3NH3+, 2.7 × 10-11

D) CH3NH2–, 2.7 × 10–11

98) Acetic acid CH3COOH, has an acid dissociation constant of 1.8 × 10-5. What is the

conjugate base of acetic acid and what is its base dissociation constant?

A) CH3C(OH)2+, 5.6 × 104

B) CH3C(OH)2+, 5.6 × 10-10

C) CH3COOH, 5.6 × 10-10

D) CH3CO2–, 5.6 × 10–10

99) Dihydrogen phosphate H2PO4–, has an acid dissociation constant of What is the

conjugate base of H2PO4– and what is its base dissociation constant?

A) H3PO4, 1.6 × 106

B) H3PO4, 1.6 × 10-8

C) HPO42-, 1.6 × 106

D) HPO42-, 1.6 × 10-8

100) Which of the following salts are acidic?

A) LiCl, NaCl, KCl

B) NH4Cl, CuCl2, AlCl3

C) NaCH3CO2, KCH3CO2, RbCH3CO2

D) NaCl, NH4Cl, Na2CO3

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

highest pH?

A) NaHSO4

B) LiClO4

C) MgO

D) CH3NH3I

102) If an equal number of moles of the weak acid HCN 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.

103) Arrange the following 0.10 M aqueous solutions in order of increasing pH: NaOH, HBr,

NaCH3CO2, KBr, NH4Br.

A) HBr, KBr, NH4Br, NaCH3CO2, NaOH

B) NaOH, NaCH3CO2, NH4Br, KBr, HBr

C) NaOH, NaCH3CO2, KBr, NH4Br, HBr

D) HBr, NH4Br, KBr, NaCH3CO2, NaOH

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

highest pH?

A) KI

B) KBr

C) KCl

D) KF

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

closest to 7.00?

A) NH4Cl

B) BaO

C) NaHSO4

D) RbI

106) Calculate the pH of a 0.100 M NaCH3CO2 solution. Ka for acetic acid, CH3CO2H, is

A) 2.87

B) 5.13

C) 8.87

D) 11.13

107) Calculate the pH of a of 0.100 M KBrO solution. Ka for hypobromous acid, HBrO, is

A) 3.15

B) 4.85

C) 9.15

D) 10.85

108) Calculate the pH of a 0.100 M CH3NH3Cl solution. Kb for methylamine, CH3NH2, is

A) 2.22

B) 5.78

C) 8.22

D) 11.78

30

109) Equal volumes of 0.10 M NH3 (Kb = 1.8 × 10-5) and 0.10 M HCN (Ka = 4.9 × 10-10) are

mixed together. Will the resulting solution be acidic, basic, or neutral?

A) acidic

B) basic

C) neutral

D) insufficient information to solve

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

lowest pH?

A) NaCl

B) NH4Cl

C) MgCl2

D) AlCl3

111) What is the identity of M in the hydrate M(H2O)6n+ that has the 0.10 M solution with the

lowest pH?

A) Li+

B) Na+

C) Mg2+

D) Al3+

112) What is the identity of M in the hydrate M(H2O)6n+ that has the 0.10 M solution with the

highest pH?

A) Li+

B) Na+

C) Mg2+

D) Al3+

31

113) What is the strongest acid among the following?

A) HF

B) HCl

C) HBr

D) HI

114) What is the strongest acid among the following?

A) H2O

B) H2S

C) H2Se

D) H2Te

115) What is the strongest acid among the following?

A) HF

B) HCl

C) H2O

D) H2S

116) What is the weakest acid among the following?

A) SiH4

B) PH3

C) H2S

D) HCl

117) Which acid of the following set has the strongest conjugate base?

A) CH4

B) NH3

C) H2O

D) HF

118) What is the strongest base among the following?

32

A) ClO–

B) ClO2–

C) ClO3–

D) ClO4–

119) What is the strongest acid among the following?

A) H2SO3

B) H2SO4

C) H2SeO3

D) H2SeO4

120) What is the strongest acid of the following?

A) HOI

B) HOBr

C) HOCl

D) All are equivalent.

121) What is the strongest acid among the following?

A) HIO

B) HIO2

C) HIO3

D) HIO4

122) What is the strongest acid among the following?

A) CH3CO2H

B) ClCH2CO2H

C) Cl2CHCO2H

D) Cl3CCO2H

123) Identify the Lewis acid that acts as a reactant in the following reaction

Fe(H2O)63+(aq) + 6 CN–(aq) → Fe(CN)63-(aq) + 6 H2O(l).

A) Fe3+

B) H2O

C) CN–

D) Fe(H2O)63+

124) Identify the Lewis acid that acts as a reactant in the following reaction

Co(H2O)63+(aq) + 6 NH3(aq) → Co(NH3)63+(aq) + 6 H2O(l).

A) Co(H2O)63+

B) Co3+

C) NH3

D) H2O

125) For Cu2+ and CO2, which will behave as a Lewis acid toward OH– in water?

A) only Cu2+

B) only CO2

C) Cu2+ and CO2

D) neither Cu2+ nor CO2

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

A) H2O

B) NH3

C) NH4+

D) Cl–

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

A) CH3NH2

B) (CH3)2NH

C) (CH3)3N

D) (CH3)3NH+

128) The compound BF3 can be described as a(n)

A) Arrhenius acid.

B) Brønsted-Lowry acid.

C) Lewis acid.

D) Lewis base.

129) Identify the set of Lewis acids.

A) BH3, BF3, Cu2+, CO2

B) Cl–, OH–, NH3, H2O

C) H3PO4, H2PO4–, HPO42-, PO43-

D) CH3–, NH2–, OH–, F–

130) Which one of the following is expected to be the strongest Lewis acid?

A) Fe

B) Fe+

C) Fe2+

D) Fe3+

In the following reaction the unshaded spheres represent H atoms.

131) Identify the Brønsted-Lowry acids.

A) (1) and (3)

B) (1)

C) (2) and (3)

D) (2) and (4)

132) Identify the Brønsted-Lowry bases.

A) (1) and (3)

B) (1) and (4)

C) (2)

D) (2) and (4)

In the following reaction the unshaded spheres represent H atoms.

133) Identify the Brønsted-Lowry acids.

A) (1) and (3)

B) (1) and (4)

C) (2)

D) (2) and (4)

134) Identify the Brønsted-Lowry bases.

A) (1) and (3)

B) (1)

C) (2) and (3)

D) (2) and (4)

In the following reaction the unshaded spheres represent H atoms.

135) Identify the Brønsted-Lowry acid/base conjugate pairs.

A) (1)/(2) and (3)/(4)

B) (1)/(3) and (2)/(4)

C) (1)/(4) and (2)/(3)

In the following reaction the unshaded spheres represent H atoms.

136) Identify the Brønsted-Lowry acid/base conjugate pairs.

A) (1)/(2) and (3)/(4)

B) (1)/(3) and (2)/(4)

C) (1)/(4) and (2)/(3)

The following pictures represent aqueous solutions of three acids HA (A = X, Y, or Z); water

molecules have been omitted for clarity.

137) Arrange the three acids in order of increasing acid strength.

A) HZ < HY < HX

B) HY < HZ < HX

C) HZ < HX < HY

D) HX < HZ < HY

138) Which acid, if any, is a strong acid?

A) All are strong acids.

B) HX and HZ

C) HY

D) None are strong acids.

139) Which acid has the smallest value of Ka?

A) HX

B) HY

C) HZ

D) All have the same Ka value.

140) Which acid has the lowest percent dissociation?

A) HX

B) HY

C) HZ

D) All have the same percent dissociation.

141) Which acid solution has the lowest pH?

A) HX

B) HY

C) HZ

D) All have the same pH.

142) Which of the above pictures represents a solution of a weak diprotic acid H2A for which

(Water molecules have been omitted for clarity.)

A) picture (a)

B) picture (b)

C) picture (c)

D) picture (d)

143) Which of the above pictures represents a solution of a diprotic acid H2A for which

and Ka2 is exceptionally small. (Water molecules have been omitted for clarity.)

A) picture (a)

B) picture (b)

C) picture (c)

D) picture (d)