Chapter 15 – Acids and Bases
130. The equilibrium constant for the reaction
C6H5COOH(aq) + CH3COO–(aq) C6H5COO–(aq) + CH3COOH(aq)
is 3.6 at 25C. If Ka for CH3COOH is 1.8 10–5, what is the acid dissociation constant for
C6H5COOH?
131. The equilibrium constant for the reaction
C7H15COOH(aq) + HCOO–(aq) C7H15COO–(aq) + HCOOH(aq)
is 7.23 10–2 at 25C. If Ka for formic acid (HCOOH) is 1.77 10–4, what is the acid
dissociation constant for C7H15COOH?
Chapter 15 – Acids and Bases
132. For maleic acid, HOOCCH=CHCOOH, Ka1 = 1.42 10–2 and Ka2 = 8.57 10–7.
What is the concentration of maleate ion (–OOCCH=CHCOO–) in a 0.150 M aqueous solution
of maleic acid?
133. Aspartic acid (C4H7NO4), one of the 20 essential amino acids, has two ionizable
hydrogens. At 25C, Ka1 = 1.38 10–4 and Ka2 = 1.51 10–10. What is the concentration of
doubly ionized aspartate ions in a 0.125 M aqueous solution of aspartic acid?
Chapter 15 – Acids and Bases
134. What mass of sodium cyanide must be added to 250. mL of water in order to obtain a
solution having a pH of 10.50? [Ka(HCN) = 4.9 10–10]
135. What mass of sodium formate (HCOONa) must be added to 350. mL of water in order to
obtain a solution having a pH of 8.50? [Ka(HCOOH) = 1.77 10–4]
Chapter 15 – Acids and Bases
136. A tablet of a common over-the-counter drug contains 200. mg of caffeine (C8H10N4O2).
What is the pH of the solution resulting from the dissolution of two of these tablets in 225.
mL of water? (For caffeine, Kb = 4.1 10–4.)
137. Morphine, C17H19NO3, is often used to control severe post-operative pain. What is the
pH of the solution made by dissolving 25.0 mg of morphine in 100. mL of water? (For
morphine, Kb = 1.62 10–6.)
Chapter 15 – Acids and Bases
138. Suppose that ammonia, applied to a field as a fertilizer, is washed into a farm pond
containing 3.0 106 L of water. If the pH of this pond is found to be 9.81, what volume of
liquid ammonia found its way into the pond? [Given: Kb(NH3) = 1.8 10–5; the density of
liquid ammonia is 0.771 g/cm3]
139. Due to a highway accident, 150 L of concentrated hydrochloric acid (12.0 M) is released
into a lake containing 5.0 105 m3 of water. If the pH of this lake was 7.0 prior to the
accident, what is the pH of the lake following the accident?
Chapter 15 – Acids and Bases
140. Select True or False: The conjugate acid-base pairs in the reaction HSO4– + HF
H2SO4 + F– are HF–F–; H2SO4–HSO4–
Bloom’s Level: 4. Analyze
Difficulty: Medium
Gradable: automatic
Section: 15.01
Subtopic: Acid-Base definitions
Topic: Acids and Bases
142. Select True or False: H3AsO3 is a stronger acid than H3AsO4.
Chapter 15 – Acids and Bases
144.
Select True or False: Al(OH)3 is an amphoteric hydroxide. The balanced ionic equation for its reaction with HNO3 is:
Al(OH)3 + 3HNO3 → Al(NO3)3 + 3H2O
145.
Select True or False: Al(OH)3 is an amphoteric hydroxide. The balanced ionic equation to show its reaction with KOH is:
Al(OH)3 + KOH → K[Al(OH)4]
Chapter 15 – Acids and Bases
147. Select True or False: The formula for the conjugate base of HPO42– is H2PO4–.
148. Select True or False: The formula for the conjugate acid of H2PO4
– is H3PO4.
Chapter 15 – Acids and Bases
150. Calculate the pH of a solution containing 0.20 g of NaOH in 2,000. mL of solution.
151. Calculate the pOH of a solution containing 0.25 g of HCl in 800. mL of solution.
Chapter 15 – Acids and Bases
152. Calculate the H+ ion concentration in a solution with a pH of 3.85.
153. If the pH of stomach acid is 1.0, what is the hydroxide ion concentration in this
solution?
Chapter 15 – Acids and Bases
154. If the pH of liquid bleach is 12.0, what is the hydroxide ion concentration in this
solution?
155. Select True or False: If the pH of pure water is 7.0, the hydroxide ion concentration in
pure water is 1 10–7 M.
Chapter 15 – Acids and Bases
156. If the pH of tomato juice is 4.0, what is the hydroxide ion concentration in this solution?
157. If the pH of seawater is 8.0, what is the hydroxide ion concentration in seawater?
Chapter 15 – Acids and Bases
158. The pH of a sample of river water is 6.0. A sample of effluent from a food processing
plant has a pH of 4.0. What is the ratio of hydronium ion concentration in the effluent to the
hydronium ion concentration in the river?
159.
Select True or False: Lime is used in farming to reduce the acidity of the soil. The chemical name for lime is calcium oxide.
When water in the soil reacts with lime, the formula of the base formed is Ca(OH)2.
160. Select True or False: The compound CH3NH2 reacts with water to form CH3NH3+ and
OH–. CH3NH2 acts as a base in this reaction.
161. Select True or False: HCN is classified as a weak acid in water. This classification means
162. Select True or False: When carbon dioxide dissolves in rain water carbonic acid forms
which raises the pH of rain water above 7.
Chapter 15 – Acids and Bases
163. When 2.0 10–2 mole of nicotinic acid (a monoprotic acid) is dissolved in 350. mL of
water, the pH is 3.05. What is the Ka of nicotinic acid?
164. A 8.0 M solution of formic acid (HCOOH) is 0.47% ionized. What is the Ka of formic
acid?
Chapter 15 – Acids and Bases
165. The pH of a 0.6 M solution of a weak acid is 4.0. What percent of the acid has ionized?
166. Write the chemical formula for the acid formed when Cl2O7 is dissolved in water.
167. Write the chemical formula for the acid formed when Cl2O5 is dissolved in water.
Chapter 15 – Acids and Bases
170. Calculate the pH of a 0.025 M solution of NaNO2. (Ka(HNO2) = 4.5 x 10-4)
Chapter 15 – Acids and Bases
171. Calculate the pH of a 0.011 M solution of NH4NO3. (Kb(NH3) = 1.8 x 10-5)
172. Calculate the pH of a 0.20 M solution of the weak base pyridine. (C5H5N; Kb = 1.7 x 10–
9)
Chapter 15 – Acids and Bases
173. Calculate the pH of a 0.15 M solution of HOI. (Ka = 2.3 x 10–11)
174. Select True or False: In the reaction HNO3 + NH3 NH4+ + NO3–, NH4+ and NH3 are a
conjugate acid-base pair.
Chapter 15 – Acids and Bases
176.
Select True or False: In the reaction Ag+(aq) + Cl–(aq) → AgCl(s), Ag+ acts as a Lewis acid.
177. Select True or False: In aqueous solutions at 25C, the sum of the ion concentrations
178. Select True or False: Kw = 1.0 x 10–14 at all temperatures.