Chapter 16 3 What The Hydrogenion Concentration Solution That

108. Which of the following solutions will not yield an effective NaH2PO4/Na2HPO4 buffer?

A)

2.0 M NaH2PO4 + 1.0 M NaOH

B)

1.0 M NaH2PO4 + 1.0 M Na2HPO4

C)

1.0 M H3PO4 + 1.0 M Na3PO4

D)

2.0 M Na2HPO4 + 1.0 M HCl

E)

1.0 M H3PO4 + 1.0 M NaH2PO4

109. Which of the following mixtures will be a buffer when dissolved in 1 L of water?

A)

0.3 mol KCl and 0.3 mol HCl

B)

0.2 mol HC2H3O2 and 0.1 mol NaOH

C)

0.4 mol NH3 and 0.4 mol HCl

D)

0.2 mol HBr and 0.1 mol NaOH

E)

0.1 mol Ba(OH)2 and 0.2 mol HCl

110. Which of the following solutions would show the greatest change in pH upon the addition of

10.0 mL of 1.0 M NaOH to 1.0 L of the solution?

A)

0.50 M HC2H3O2

B)

0.50 M HC2H3O2 + 0.50 M NaC2H3O2

C)

0.10 M HC2H3O2 + 0.10 M NaC2H3O2

D)

0.10 M HC2H3O2

E)

0.50 M NaC2H3O2

111. Which of the following mixtures will be a buffer when dissolved in a liter of water?

A)

0.4 mol NH3 and 0.4 mol HCl

B)

0.3 mol NaCl and 0.3 mol HCl

C)

0.1 mol Ca(OH)2 and 0.3 mol HI

D)

0.2 mol H3PO4 and 0.1 mol NaOH

E)

0.2 mol HBr and 0.1 mol NaOH

Test Bank General Chemistry, 10th edition 35

112. A weak acid, HF, is in solution with dissolved sodium fluoride, NaF. If HCl is added, which

ion will react with the extra hydrogen ions from the HCl to keep the pH from changing?

A)

Na+

B)

OH–

C)

Na–

D)

F–

E)

none of these

113. Suppose a buffer solution is made from formic acid (HCHO2) and sodium formate

(NaCHO2). What is the net ionic equation for the reaction that occurs when a small amount

of hydrochloric acid is added to the buffer?

A)

H3O+(aq) + HCHO2(aq) → H2O(l) + H2CHO2+(aq)

B)

H3O+(aq) + CHO2–(aq) → HCHO2(aq) + H2O(l)

C)

HCl(aq) + CHO2–(aq) → HCHO2(aq) + Cl–(aq)

D)

HCl(aq) + OH–(aq) → H2O(l) + Cl–(aq)

E)

H3O+(aq) + OH–(aq) → 2H2O(l)

114. Suppose a buffer solution is made from formic acid (HCHO2) and sodium formate

(NaCHO2). What is the net ionic equation for the reaction that occurs when a small amount

of sodium hydroxide is added to the buffer?

A)

NaOH(aq) + HCHO2(aq) → NaCHO2(aq) + H2O(l)

B)

Na+(aq) + HCHO2(aq) → NaH(aq) + HCO2+(aq)

C)

OH–(aq) + HCHO2(aq) → CHO2–(aq) + H2O(l)

D)

H3O+(aq) + OH–(aq) → 2H2O(l)

E)

NaOH(aq) + H3O+(aq) → Na+(aq) + 2H2O(l)

115. What is the pH of a solution that is 0.12 M in acetic acid, HC2H3O2, and 0.50 M in sodium

acetate, NaC2H3O2, at 25°C? Ka of acetic acid is 1.8  10–5.

A)

4.12

B)

1.53

C)

4.74

D)

2.29

E)

5.36

116. What is the hydrogen-ion concentration of a solution that is 0.052 M in acetic acid and 0.052

M in sodium acetate at 25°C? The acid-ionization constant of acetic acid is 1.8  10–5 at

25°C.

A)

1.8  10–3 M

B)

1.8  10–6 M

C)

1.8  10–7 M

D)

1.8  10–5 M

E)

1.8  10–4 M

117. What is the pH of a buffer made by combining 175 mL of 0.33 M NaC2H3O2 with 126 mL

of 0.48 M HC2H3O2? The Ka of acetic acid is 1.75  10-5.

A)

4.74

B)

4.78

C)

5.79

D)

4.69

E)

5.24

118. What is the hydronium-ion concentration of a buffer solution that is 0.50 M Na2HPO4 and

0.20 M NaH2PO4? For H3PO4, Ka1 = 6.9  10–3, Ka2 = 6.2  10–8, and Ka3 = 4.8  10–13.

A)

1.7  10–2 M

B)

2.8  10–3 M

C)

1.6  10–7 M

D)

2.5  10–8 M

E)

1.9  10–13 M

Test Bank General Chemistry, 10th edition 37

119. What mass of sodium hydroxide must be added to 75.0 mL of 0.205 M acetic acid in order

to create a buffer with a pH of 4.74? Ka for acetic acid is 1.8  10–5.

A)

40 g

B)

0.31 g

C)

1.0 g

D)

0.000055 g

E)

0.61 g

120. What is the hydronium-ion concentration in a solution resulting from mixing 173 mL of

0.100 M HCN and 73 mL of 0.100 M KOH at 25°C? Ka for HCN = 4.9  10–10 at 25°C.

A)

4.5  10–6 M

B)

7.0  10–6 M

C)

3.4  10–13 M

D)

6.7  10–10 M

E)

1.0  10–13 M

121. What is the pH of a solution that is 0.026 M in HA and also 0.0060 M in NaA?

(Ka = 5.3  10–6)

A)

8.15

B)

4.64

C)

5.91

D)

5.28

E)

7.70

122. A certain weak base B has a base-ionization constant Kb of 2.4  10–4 at 25°C. If strong

acid is added to a solution of B, at what pH will [B] = [BH+]?

A)

8.5

B)

10.4

C)

7.0

D)

3.6

E)

5.5

123. What molar ratio of acetic acid to sodium acetate is required to create a buffer solution

having a pH of 4.89 at 25°C? Ka for HC2H3O2 is 1.8  10–5.

A)

0.72

B)

1.4

C)

0.56

D)

2.0

E)

2.9

124. What is the hydronium-ion concentration of a solution formed by combining 400. mL of

0.21 M HNO3 with 600. mL of 0.11 M NaOH at 25°C?

A)

0.082 M

B)

6.7  10–13 M

C)

0.21 M

D)

0.018 M

E)

0.11 M

125. What is the hydronium-ion concentration of a solution formed by combining 700. mL of

0.18 M HCl with 300. mL of 0.51 M NaOH at 25°C?

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

A)

0.13 M

B)

3.7  10–13 M

C)

0.33 M

D)

0.18 M

E)

0.027 M

126. What is the pH of a solution that is formed at 25°C by combining 300 mL of 0.040 M NaOH

with 400 mL of 0.030 M HCl?

A)

2.0

B)

3.0

C)

5.0

D)

7.0

E)

1.0

127. What is the hydronium-ion concentration of a solution that is formed by combining 600. mL

of 0.10 M NaOH with 400. mL of 0.80 M HNO3 at 25°C?

A)

0.080 M

B)

0.010 M

C)

0.80 M

D)

0.45 M

E)

0.26 M

128. Which of the following statements is true concerning the titration of a weak monoprotic acid

with a strong base?

A)

At the equivalence point, the solution has excess moles of strong base.

B)

At the equivalence point, the solution is acidic.

C)

At the equivalence point, the solution has excess moles of weak acid.

D)

At the equivalence point, the solution is composed of the conjugate base of the

weak acid.

E)

At the equivalence point, the pH is 7.

129. What is the pH at the equivalence point of the titration of a strong acid with a strong base?

A)

3.9

B)

4.5

C)

8.2

D)

7.0

E)

none of these

Test Bank General Chemistry, 10th edition 40

130. Which of the following indicators is most suitable for the titration of a 25.00-mL sample of

0.140 M propionic acid, HC3H5O2, with strong base?

A)

alizarin yellow (transition pH range: 10.0–12.0)

B)

methyl red (transition pH range: 4.2–6.3)

C)

methyl orange (transition pH range: 3.1–4.4)

D)

thymol blue (transition pH range: 8.0–9.6)

E)

bromothymol blue (transition pH range: 6.2–7.6)

131. A solution contains 10. mmol of H3PO4 and 5.0 mmol of NaH2PO4. How many milliliters of

0.10 M NaOH must be added to reach the second equivalence point of the titration of the

H3PO4 with NaOH?

A)

250 mL

B)

2.0  102 mL

C)

50 mL

D)

150 mL

E)

1.0  102 mL

132. A 75.0-mL sample of 0.0500 M HCN (Ka = 6.2 10–10) is titrated with 0.421 M NaOH.

What is [H+] in the solution after 3.0 mL of 0.421 M NaOH has been added?

A)

8.2  10–6 M

B)

2.0 M

C)

1.2  10–9 M

D)

1.0  10–7 M

E)

none of these

133. If 40 mL of 0.10 M NaOH is added to 50 mL of 0.20 M HC2H3O2, what is the pH of the

resulting solution at 25°C? Ka for HC2H3O2 is 1.8  10–5 at 25°C.

A)

10.5

B)

4.3

C)

4.9

D)

2.7

E)

4.6

Test Bank General Chemistry, 10th edition 41

134. A 25.00-mL sample of propionic acid, HC3H5O2, of unknown concentration was titrated

with 0.155 M KOH. The equivalence point was reached when 35.94 mL of base had been

added. What was the original concentration of the propionic acid?

A)

0.295 M

B)

0.111 M

C)

0.108 M

D)

0.155 M

E)

0.223 M

135. A 25.00-mL sample of propionic acid, HC3H5O2, of unknown concentration was titrated

with 0.101 M KOH. The equivalence point was reached when 42.20 mL of base had been

added. What is the concentration of the propionate ion at the equivalence point?

A)

0.101 M

B)

0.147 M

C)

0.0634 M

D)

0.170 M

E)

0.128 M

136. A 25.00-mL sample of propionic acid, HC3H5O2, of unknown concentration was titrated

with 0.151 M KOH. The equivalence point was reached when 41.28 mL of base had been

added. What is the hydroxide-ion concentration at the equivalence point? Ka for propionic

acid is 1.3  10–5 at 25°C.

A)

1.5  10-9 M

B)

1.0  10-7 M

C)

1.1  10-5 M

D)

8.5  10-6 M

E)

1.1  10-3 M

Test Bank General Chemistry, 10th edition 42

137. Which acid-base combination is depicted by this titration curve?

A)

Titration of a weak acid with a strong base.

B)

Titration of a weak base with a strong acid.

C)

Titration of a strong acid with a strong base.

D)

Titration of a strong base with a strong acid.

E)

Not enough information provided.

138. The following titration curve depicts the titration of a weak acid with a strong base. Which

of the labeled points is/are part of the buffer region.

Test Bank General Chemistry, 10th edition 43

A)

II only

B)

III only

C)

I only

D)

II and V

E)

I and IV

139. A sample of ammonia (Kb = 1.8  10–5) is titrated with 0.1 M HCl. At the equivalence point,

what is the approximate pH of the solution?

A)

5

B)

1

C)

9

D)

7

E)

11

140. A weak base is titrated with a hydrochloric acid solution. What is the pH at the equivalence

point?

A)

equal to pKa

B)

equal to 7

C)

equal to pKb

D)

greater than 7

E)

less than 7

141. Which of the following statements is true concerning the titration of a weak base by a

solution of hydrochloric acid?

A)

The solution is basic at the equivalence point.

B)

The solution is acidic at the equivalence point.

C)

At the equivalence point, the pH is determined by the hydrolysis of chloride ion.

D)

At the equivalence point, the pH is 7.

E)

At the equivalence point, there is excess hydrochloric acid.

142. Consider the titration of 300.0 mL of 0.410 M NH3 (Kb = 1.8 10–5) with 0.500 M HNO3.

After 150.0 mL of 0.500 M HNO3 has been added, what is the pH of the solution?

A)

4.94

B)

9.06

C)

6.06

D)

11.06

E)

none of these

143. Titration of 0.4089 g of an unknown monoprotic acid dissolved in 25.00 mL of water

requires 28.45 mL of 0.1521 M NaOH to reach the endpoint. What is the molar mass of the

acid?

A)

94.49 g/mol

B)

0.01058 g/mol

C)

107.5 g/mol

D)

2.186 g/mol

E)

2.718 g/mol

144. In the titration of a weak monoprotic acid with a strong base, the pH of the titration solution

halfway to the endpoint will be

A)

equal to the pKa of the weak acid.

B)

greater than 7.00.

C)

equal to 7.00.

D)

greater than the pKa of the weak acid.

E)

less than the pKa of the weak acid.

145. In the titration of a weak monoprotic acid with a strong base, the pH at the endpoint will be

A)

equal to the pKa of the weak acid.

B)

greater than 7.00.

C)

equal to 7.00.

D)

less than 7.00.

E)

less than the pKa of the weak acid.

146. In the titration of a weak monoprotic acid with a strong base, the pH at the endpoint will be

A)

equal to the pKa of the weak acid.

B)

less than 7.00.

C)

equal to 7.00.

D)

greater than the pKa of the weak acid.

E)

less than the pKa of the weak acid.