Chapter 14 2 The pain killer morphine is a weak base when added to

pH of a solution MSC: Quantitative

77. The pain killer morphine is a weak base when added to water. The Kb is 1.6  10–6. What is

the pH of a 4.33  10–3 M solution of morphine?

A)

4.08

B)

9.92

C)

5.84

D)

9.77

E)

none of these

78. The [OH–] in a 0.87 M pyridine (C5H5N; Kb = 1.7  10–9) solution is

A)

1.5  10–9 M

B)

3.8  10–5 M

C)

0.87 M

D)

4.4  10–5 M

E)

none of these

79. Calculate the pH of a 5.7 M solution of aniline (C6H5NH2; Kb = 3.8  10–10):

A)

4.33

B)

9.67

C)

5.34

D)

8.66

E)

none of these

80. Calculate the pH of a 0.69 M solution of pyridine (C5H5N; Kb = 1.7  10–9):

A)

4.47

B)

5.07

C)

9.53

D)

8.93

E)

none of these

81. Calculate the percentage of pyridine (C5H5N) that forms pyridinium ion, C5H6N+, in a 0.72

M aqueous solution of pyridine (Kb = 1.7  10–9).

A)

1.7  10–7 %

B)

3.5  10–3 %

C)

2.4  10–7 %

D)

6.7  10–3 %

E)

4.9  10–3 %

82. Which of the following aqueous solutions will have the highest pH? For NH3, Kb = 1.8  10–

5; for C2H3O2–, Kb = 5.6  10–10.

A)

2.0 M NaOH

B)

2.0 M NH3

C)

2.0 M HC2H3O2

D)

2.0 M HCl

E)

all the same

83. Calculate the pH of a 0.47 M NH3 (Kb = 1.8  10–5) solution.

A)

2.54

B)

8.93

C)

5.07

D)

0.47

E)

11.46

84. The equilibrium constant for the reaction NH4+ + OH– NH3 + H2O is:

A)

B)

C)

D)

E)

85. The pH of a 0.150 M solution of a weak base is 10.98. Calculate the pH of a 0.0603 M

solution of the base.

A)

3.22

B)

10.78

C)

7.57

D)

6.43

E)

none of these

86. Calculate the pH of the following aqueous solution:

0.52 M aniline (pKb = 9.42)

A)

4.85

B)

4.30

C)

9.70

D)

9.15

E)

none of these

87. Calculate the pH of the following aqueous solution:

0.62 M H2S (pKa1 = 7.00; pKa2 = 12.89)

A)

10.40

B)

3.60

C)

7.21

D)

6.79

E)

none of these

88. Determine the pH of a 0.034 M solution of H2SO4. The dissociation occurs in two steps. Ka1

is extremely large; Ka2 is 1.2  10–2.

A)

12.66

B)

1.47

C)

1.92

D)

1.38

E)

2.12

89. Calculate the pH of the following aqueous solution: 0.5 M H2CO3 (pKa1 = 6.37;

pKa2 = 10.25). Choose your answer from the following pH ranges:

A)

pH 0.00–2.99

B)

pH 3.00–5.99

C)

pH 6.00–8.99

D)

pH 9.00 –10.99

E)

pH 11.00–14.00

90. A 0.33-mol sample of a diprotic acid, H2A, is dissolved in 250 mL of water. The Ka1 of this

acid is 1.0  10–5 and Ka2 is 1.0  10–10. Calculate the concentration of A2– in this solution.

A)

1.0  10–5 M

B)

1.8  10–3 M

C)

3.6  10–3 M

D)

1.0  10–10 M

E)

1.32 M

91. For the stepwise dissociation of aqueous H3PO4, which of the following is not a conjugate

acid–base pair?

A)

HPO42– and PO43–

B)

H3PO4 and H2PO4–

C)

H2PO4– and HPO42–

D)

H2PO4– and PO43–

E)

H3O+ and H2O

92. The pH of a solution of 1.9 M H2A (Ka1 = 1.0  10–6 and Ka2 is 1.0  10–10) is:

A)

10.00

B)

5.72

C)

11.14

D)

2.86

E)

none of these

93. Calculate the pH of a 0.04 M solution of ascorbic acid (Ka1 = 7.9  10–5; Ka2 is 1.6  10–12).

A)

11.2

B)

2.8

C)

5.5

D)

8.5

E)

11.8

94. The dihydrogenphosphate ion, H2PO4–, has both a conjugate acid and a conjugate base.

These are, respectively:

A)

H3PO4, PO43–

B)

H3PO4, HPO42–

C)

H2PO4–, HPO42–

D)

HPO42–, PO43–

E)

HPO42–, H3PO4

95. For which of the following 0.10 M diprotic acids would the second dissociation affect the

pH significantly?

A)

H2A; Ka1 = 4.2  10–2, Ka2 = 1.8  10–7

B)

H2B; Ka1 = 2.4  10–4, Ka2 = 6.1  10–8

C)

H2C; Ka1 = 1.3  10–4, Ka2 = 5.2  10–9

D)

H2D; Ka1 = 1.8  10–3, Ka2 = 9.3  10–4

E)

The second dissociation never affects the pH significantly.

96. The conjugate acid and conjugate base of bicarbonate ion, HCO3–, are, respectively:

A)

H3O+ and OH–

B)

H3O+ and CO32–

C)

H2CO3 and OH–

D)

H2CO3 and CO32–

E)

CO32– and OH–

97. Which of the following species is present in the greatest concentration in a 0.100 M H2SO4

solution in H2O?

A)

H3O+

B)

HSO4–

C)

H2SO4

D)

All species are in equilibrium and therefore have the same concentration.

E)

SO42–

98. Which of the following is true about the pH of a solution of sulfuric acid?

A)

If the solution is dilute the pH can not be calculated.

B)

If the solution is dilute the pH is completely controlled by the first dissociation.

C)

If the solution is dilute the pH is completely controlled by the second dissociation.

D)

If the solution is concentrated the pH is partially controlled by the second

dissociation.

E)

If the solution is dilute the pH is partially controlled by the second dissociation.

99. What is the equilibrium concentration of PO43– in a 0.511 M solution of H3PO4(aq)?

(Ka1 = 7.5  10–3, Ka2 = 6.2  10–8, Ka3 = 4.8  10–13)

A)

5.8  10–2 M

B)

1.8  10–4 M

C)

4.8  10–13 M

D)

5.0  10–7 M

E)

6.2  10–8 M

100. What is the equilibrium concentration of HPO42– in a 0.528 M solution of H3PO4(aq)?

(Ka1 = 7.5  10–3, Ka2 = 6.2  10–8, Ka3 = 4.8  10–13)

A)

1.8  10–4 M

B)

5.9  10–2 M

C)

4.8  10–13 M

D)

6.2  10–8 M

E)

5.0  10–7 M

101. What is the equilibrium concentration of H2PO4– in a 0.202 M solution of H3PO4(aq)?

(Ka1 = 7.5  10–3, Ka2 = 6.2  10–8, Ka3 = 4.8  10–13)

A)

1.1  10–4 M

B)

3.5  10–2 M

C)

3.9  10–2 M

D)

7.5  10–3 M

E)

6.2  10–8 M

102. What is the equilibrium pH of a 0.835 M solution of H3PO4(aq)? (Ka1 = 7.5  10–3, Ka2 = 6.2

 10–8, Ka3 = 4.8  10–13)

A)

1.12

B)

3.64

C)

12.32

D)

6.20

E)

7.21

103. Carbonic acid is a diprotic acid, H2CO3, with Ka1 = 4.2  10–7 and Ka2 = 4.8  10–11 at 25°C.

The ion product for water is Kw = 1.0  10–14 at 25°C. What is the OH– concentration of a

solution that is 0.18 M in Na2CO3?

A)

6.1  10–3 M

B)

2.1  10–4 M

C)

6.5  10–5 M

D)

2.9  10–6 M

E)

2.7  10–4 M

104. The two acid dissociation constants for carbonic acid, H2CO3, are 4.3  10–7 and 4.8  10–11

at 25°C. The base constant, Kb, or hydrolysis constant for HCO3– is:

A)

4.3  10–7

B)

4.8  10–11

C)

2.1  10–17

D)

2.3  10–8

E)

6.2  10–22

105.

HOAc

Ka = 1.8  10–5

H2CO3

Ka1 = 4.3  10–7

Ka2 = 5.6  10–11

Which of the following 0.01 M solutions has the highest pH?

A)

HOAc

B)

NaOAc

C)

Na2CO3

D)

H2CO3

E)

NaHCO3

106. The sodium salt, NaA, of a weak acid is dissolved in water; no other substance is added.

Which of these statements (to a close approximation) is true?

A)

[H+] = [A–]

B)

[H+] = [OH–]

C)

[A–] = [OH–]

D)

[HA] = [OH–]

E)

none of these

107. Which of the following would give the highest pH when dissolved in water to form a 0.10 M

solution?

A)

a strong acid

B)

a weak acid

C)

the potassium salt of a weak acid

D)

the potassium salt of a strong acid

E)

the ammonium salt of a strong acid

Select the answer that best describes an aqueous solution made from each of the following

substances:

108. solid sodium nitrate (NaNO3)

A)

acidic

B)

basic

C)

neutral

D)

cannot tell

E)

none of these (A-D)

109. solid aluminum chloride (AlCl3)

A)

acidic

B)

basic

C)

neutral

D)

cannot tell

E)

none of these (A-D)

110. solid sodium carbonate (Na2CO3)

A)

acidic

B)

basic

C)

neutral

D)

cannot tell

E)

none of these (A-D)

111. solid ammonium acetate (NH4C2H3O2). For NH4+, Ka = 5.6  10–10; for C2H3O2–,

Kb = 5.6  10–10.

A)

acidic

B)

basic

C)

neutral

D)

cannot tell

E)

none of these (A-D)

112. solid ammonium perchlorate (NH4ClO4) For NH4+, Ka = 5.6  10–10; for ClO4–, Kb  10–21.

A)

acidic

B)

basic

C)

neutral

D)

cannot tell

E)

none of these (A-D)

113. Which of the following correctly labels the salts?

HF (Ka = 7.2  10–4)

NH3 (Kb = 1.8  10–5)

HCN (Ka = 6.2  10–10)

A)

NaCN = acidic, NH4F = basic, KCN = neutral

B)

NaCN = acidic, NH4F = neutral, KCN = basic

C)

NaCN = basic, NH4F = basic, KCN= neutral

D)

NaCN = basic, NH4F = neutral, KCN = basic

E)

NaCN = basic, NH4F = acidic, KCN = basic

114. The pH of a 1.0 M aqueous solution of NaCl is:

A)

7.0

B)

greater than 7.0

C)

less than 7.0

D)

not enough information given

E)

none of these (A-D)

115. The pH of a 1.0 M sodium acetate solution is:

A)

7.0

B)

greater than 7.0

C)

less than 7.0

D)

not enough information given

E)

none of these (A-D)

116. Calculate the pH of the following aqueous solution:

0.35 M NaF (pKa for HF = 3.14)

A)

5.66

B)

2.68

C)

8.34

D)

11.32

E)

none of these

117. Calculate the pH of the following aqueous solution:

0.39 M NH4Cl (pKb for NH3 = 4.74)

A)

9.17

B)

4.83

C)

9.67

D)

4.33

E)

none of these

acid-base properties of salt solutions | pH of a salt solution MSC: Quantitative

118. Calculate the [H+] in 1.0 M solution of Na2CO3 (for H2CO3, Ka1 = 4.3  10–7; Ka2 = 5.6  10–

11).

A)

7.5  10–6 M

B)

6.6  10–4 M

C)

1.3  10–2 M

D)

7.5  10–13 M

E)

none of these

119. The [H3O+] of a 0.49 M solution of NH4Cl in H2O at 25°C is (Kb for NH3 = 1.8  10–5):

A)

2.7  10–10 M

B)

3.0  10–3 M

C)

1.6  10–5 M

D)

0.49 M

E)

none of these

120. Calculate the pH of a 0.59 M solution of NH4Cl. (Kb for NH3 = 1.8  10–5)

A)

9.26

B)

4.74

C)

9.48

D)

4.52

E)

0.23

121. What is the pH of a 0.73 M KCl solution?

A)

0.14

B)

7.00

C)

13.86

D)

3.65

E)

9.20

122. Calculate the pH of a 0.49 M solution of NaC2H3O2 (for HC2H3O2 Ka = 1.8  10–5).

A)

4.78

B)

9.22

C)

8.95

D)

5.05

E)

none of these

123. Given that the Ka for HOCl is 3.45  10–8, calculate the K value for the reaction of HOCl

with OH–.

A)

3.45  106

B)

3.45

C)

3.45  10–22

D)

2.90  10–7

E)

2.90  1021

124. Which of the following is the correct order for increasing pHs for equimolar solutions of

HNO3, KCl, NH4Cl, KOH, and NaC2H3O2? (Ka for HC2H3O2 is 1.80  10–5, Ka for NH4+ is

5.56  10–10).

A)

KCl, NH4Cl, HNO3, KOH, NaC2H3O2

B)

HNO3, KCl, NH4Cl, KOH, NaC2H3O2

C)

NH4Cl, HNO3, KCl, KOH, NaC2H3O2

D)

HNO3, NH4Cl, KCl, NaC2H3O2, KOH

E)

none of these

125. Which of the following is the strongest base? (Kb for NH3 is 1.8  10–5, Ka2 for H2SO4 is

1.2  10–2, Ka3 for H3PO4 is 4.8  10–13)

NH3, HSO4–, PO43–, or NO3–

A)

NH3

B)

HSO4–

C)

NO3–

D)

PO43–

E)

Two of these are equally strong.

126. The salt BX, when dissolved in water, produces an acidic solution. Which of the following

could be true?

A)

HX is a weak acid.

B)

HX is a strong acid.

C)

The cation B+ is a weak acid.

D)

All of the above could be true.

E)

Only A and C could be true.

127. Calculate the Ka for an unknown monoprotic acid HX, given that a solution of 0.28 M LiX

has a pH of 8.90.

A)

2.3  10–10

B)

3.5  10–10

C)

1.8  103

D)

8.9  10–5

E)

4.4  10–5

128. If Ka for HCN is 6.17  10–10, what is Kb for CN–?

Note: CN– + H2O HCN + OH–

A)

6.17  10–24

B)

6.17  104

C)

1.62  10–5

D)

1.23  10–9

E)

none of these

129. A 0.186 M solution of the salt NaA has a pH of 8.40. Calculate the Ka value of the acid HA.

A)

3.4  10–11

B)

7.4  10–10

C)

2.9  10–4

D)

1.2  102

E)

none of these

130. If you know Kb for ammonia, NH3, you can calculate the equilibrium constant, Ka, for the

following reaction: NH4+ NH3 + H+ by the equation:

A)

Ka = Kw  Kb

B)

Ka = Kw / Kb

C)

Ka = 1 / Kb

D)

Ka = Kb / Kw

E)

none of these

131. The hydrogen halides (HF, HCl, HBr, and HI) are all polar molecules. The strength of the

acid each forms in water is based on which of the following?

A)

the polarity of the molecule

B)

the size of the molecule

C)

the strength of the bond

D)

two of these

E)

none of these

132. Which factor listed below is most important in determining the strength of an oxyacid?

A)

the size of the molecule

B)

the ability of the molecule to change atomic orientation

C)

the identity of the central atom in the molecule

D)

the number of oxygen atoms present in the molecule

E)

none of these

133. Which is the strongest acid of the following?

A)

HClO2

B)

HClO

C)

HBrO

D)

HIO

E)

HOAt

134. Which of the following would produce a basic aqueous solution?

A)

P4O10

B)

KCl

C)

CO2

D)

NH4Cl

E)

none of these

135. Calculate the pH of a 0.005 M solution of potassium oxide, K2O.

A)

12.0

B)

11.7

C)

7.0

D)

2.3

E)

2.0

136. Which of the species below, when dissolved in H2O, will not produce a basic solution?

A)

SO2

B)

NH3

C)

BaO

D)

Ba(OH)2

E)

none of these

137. Which of the following species cannot act as a Lewis base?

A)

O2–

B)

OH–

C)

CH4

D)

H2S

E)

NH3

138. Which of the following species cannot act as a Lewis base?

A)

Al3+

B)

O2–

C)

OH–

D)

H2O

E)

H2O2

139. Which of the following species cannot act as a Lewis base?

A)

N3–

B)

NH2–

C)

NH2–

D)

NH3

E)

NH4+

140. Which of the following species cannot act as a Lewis acid?

A)

K+

B)

Mg2+

C)

Al3+

D)

H+

E)

H–

141. Which of the following species cannot act as a Lewis acid?

A)

NH4+

B)

H+

C)

BF3

D)

BeCl2

E)

Ag+

142. In the reaction:

CaO(s) + SO2(g) → CaSO3(s)

A)

Ca2+ acts as a Lewis acid and SO32– acts as a Lewis base.

B)

O2– acts as a Lewis base and SO2 acts as a Lewis acid.

C)

O2– acts as a Lewis base and Ca2+ acts as a Lewis acid.

D)

CaO is the Lewis acid and CaSO3 is its conjugate base.

E)

SO2 is the Lewis acid and CaSO3 is its conjugate base.

143. Consider the following reaction:

AgBr(s) + 2CN–(aq) → Ag(CN)2–(aq) + Br–(aq)

The species that are acting as a Lewis acid and Lewis base, respectively, are

A)

AgBr and Ag(CN)2–

B)

Ag(CN)2– and Ag+

C)

Ag+ and Br–

D)

Br– and CN–

E)

Ag+ and CN–

144. Define amphoteric substance.

145. Explain why 0.1 M NaCN is basic while 0.1 M NaNO3 is neutral.

146. Explain why Al2(SO4)3 produces an acidic solution when it is dissolved in water.

147. K2O

148. NO2

149. Cl2O

150. CaO

151. SO2