2 MAXE · 401 MEHC
★
University of Wisconsin–Madison
College of Letters & Science — Department of Chemistry
NUMEN LUMEN
EST. 1848
NUMEN LUMEN · GOD, OUR LIGHT
CHEM 104 EXAM 2
E Q U I L I B R I U M · AC I D S & B A S E S · B U F F E RS · T I T RAT I O N S · S O LU B I L I TY
INSTITUTION University of Wisconsin–Madison COURSE CODE CHEM 104
PROGRAM Bachelor of Science — General ACADEMIC YEAR
Chemistry Sequence
EXAM TITLE CHEM 104 EXAM 2 TOTAL QUESTIONS 131 Questions
COURSE TITLE General Chemistry II FORMAT Multiple Choice — Select the
Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question.
▸ Equilibrium constants, Le Chatelier's principle, acid-base theories, buffer systems, titration curves, and
solubility equilibria are core testable content.
▸ ICE table calculations, pH/pKa relationships, and Ksp problems are emphasized.
▸ Correct answers and clinical/academic rationales appear below each question for review.
▸ All content reflects CHEM 104 General Chemistry II — Exam 2 learning objectives.
, SECTION I — EQUILIBRIUM, ACIDS & BASES, BUFFERS,
Questions 1 – 131
TITRATIONS, SOLUBILITY
1. According to the Arrhenius definition, an acid is a substance that does what in aqueous
solution?
A. Increases the concentration of hydroxide ions
B. Increases the concentration of hydronium ions/protons
C. Donates a lone pair of electrons
D. Decreases the concentration of all ions
CORRECT ANSWER B — Increases the concentration of hydronium ions/protons
RATIONALE An Arrhenius acid is a substance that increases the concentration of hydronium
ions (H₃O⁺) or protons (H⁺) in aqueous solution. This is the oldest and most
restrictive acid definition. An Arrhenius base (A) increases OH⁻ concentration. A
Lewis base (C) donates an electron pair. Option D is incorrect — acids increase,
not decrease, ion concentration.
2. A student compares two weak acids: Acid A has a pKa of 3.2, and Acid B has a pKa of 9.5.
Which statement correctly relates pKa to acid strength?
A. Higher pKa means stronger acid; Acid B is stronger
B. Higher pKa means weaker acid; Acid A is stronger
C. pKa is unrelated to acid strength
D. Both acids have equal strength because both are weak acids
CORRECT ANSWER B — Higher pKa means weaker acid; Acid A is stronger
RATIONALE pKa = −log(Ka). The higher the pKa, the smaller the Ka, and the weaker the acid.
Acid A (pKa 3.2) is stronger than Acid B (pKa 9.5) because it has a lower pKa and
therefore a larger Ka. This inverse logarithmic relationship is fundamental to
comparing acid strengths. A strong acid like HCl has a very low (even negative)
pKa.
,3. The equilibrium constant for the dissolution of a sparingly soluble ionic compound is
called:
A. Ka — acid dissociation constant
B. Kb — base dissociation constant
C. Ksp — solubility product constant
D. Kw — ion product constant for water
CORRECT ANSWER C — Ksp — solubility product constant
RATIONALE Ksp is the solubility product constant — the equilibrium constant for the
dissolution of a sparingly soluble ionic solid into its constituent ions in aqueous
solution. For example, AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq), Ksp = [Ag⁺][Cl⁻]. Ka (A) is for
acid dissociation. Kb (B) is for base dissociation. Kw (D) is the ion product
constant of water (1.0×10⁻¹⁴ at 25°C).
4. For the reaction A ⇌ B, the forward equilibrium constant is K = 4.0. What is the equilibrium
constant for the reverse reaction B ⇌ A?
A. 4.0
B. −4.0
C. 0.25
D. 16.0
CORRECT ANSWER C — 0.25
RATIONALE The equilibrium constant for a reverse reaction is the reciprocal of the forward
equilibrium constant: K_reverse = 1/K_forward. K = 4.0, so K_reverse = 1/4.0 =
0.25. This relationship holds because the products of the forward reaction
become the reactants of the reverse reaction, inverting the equilibrium
expression.
, 5. Which of the following is NOT one of the seven common strong acids?
A. HCl — hydrochloric acid
B. HNO₃ — nitric acid
C. HF — hydrofluoric acid
D. H₂SO₄ — sulfuric acid
CORRECT ANSWER C — HF — hydrofluoric acid
RATIONALE The seven strong acids are HCl, HBr, HI, HClO₃, HClO₄, HNO₃, and H₂SO₄. HF
(hydrofluoric acid) is notably a weak acid despite being a halogen acid — it only
partially ionizes in water due to the strong H–F bond. This is a common
misconception. All other options listed (HCl, HNO₃, H₂SO₄) are strong acids that
dissociate completely.
6. Le Chatelier's principle states that when stress is applied to a system at equilibrium, the
system will shift to relieve that stress. Which of the following are examples of such
stressors?
A. Concentration, temperature, pressure, and presence of a catalyst
B. Only concentration changes
C. Only temperature changes
D. Only pressure changes for gas reactions
CORRECT ANSWER A — Concentration, temperature, pressure, and presence of a catalyst
RATIONALE Stressors that can disturb a system at equilibrium include changes in
concentration (adding or removing reactants/products), temperature (exothermic
vs endothermic shifts), pressure (for gaseous systems with unequal moles of gas),
and the presence of a catalyst. Note: a catalyst speeds up the rate of reaching
equilibrium but does NOT shift the equilibrium position — it affects kinetics, not
thermodynamics.
★
University of Wisconsin–Madison
College of Letters & Science — Department of Chemistry
NUMEN LUMEN
EST. 1848
NUMEN LUMEN · GOD, OUR LIGHT
CHEM 104 EXAM 2
E Q U I L I B R I U M · AC I D S & B A S E S · B U F F E RS · T I T RAT I O N S · S O LU B I L I TY
INSTITUTION University of Wisconsin–Madison COURSE CODE CHEM 104
PROGRAM Bachelor of Science — General ACADEMIC YEAR
Chemistry Sequence
EXAM TITLE CHEM 104 EXAM 2 TOTAL QUESTIONS 131 Questions
COURSE TITLE General Chemistry II FORMAT Multiple Choice — Select the
Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question.
▸ Equilibrium constants, Le Chatelier's principle, acid-base theories, buffer systems, titration curves, and
solubility equilibria are core testable content.
▸ ICE table calculations, pH/pKa relationships, and Ksp problems are emphasized.
▸ Correct answers and clinical/academic rationales appear below each question for review.
▸ All content reflects CHEM 104 General Chemistry II — Exam 2 learning objectives.
, SECTION I — EQUILIBRIUM, ACIDS & BASES, BUFFERS,
Questions 1 – 131
TITRATIONS, SOLUBILITY
1. According to the Arrhenius definition, an acid is a substance that does what in aqueous
solution?
A. Increases the concentration of hydroxide ions
B. Increases the concentration of hydronium ions/protons
C. Donates a lone pair of electrons
D. Decreases the concentration of all ions
CORRECT ANSWER B — Increases the concentration of hydronium ions/protons
RATIONALE An Arrhenius acid is a substance that increases the concentration of hydronium
ions (H₃O⁺) or protons (H⁺) in aqueous solution. This is the oldest and most
restrictive acid definition. An Arrhenius base (A) increases OH⁻ concentration. A
Lewis base (C) donates an electron pair. Option D is incorrect — acids increase,
not decrease, ion concentration.
2. A student compares two weak acids: Acid A has a pKa of 3.2, and Acid B has a pKa of 9.5.
Which statement correctly relates pKa to acid strength?
A. Higher pKa means stronger acid; Acid B is stronger
B. Higher pKa means weaker acid; Acid A is stronger
C. pKa is unrelated to acid strength
D. Both acids have equal strength because both are weak acids
CORRECT ANSWER B — Higher pKa means weaker acid; Acid A is stronger
RATIONALE pKa = −log(Ka). The higher the pKa, the smaller the Ka, and the weaker the acid.
Acid A (pKa 3.2) is stronger than Acid B (pKa 9.5) because it has a lower pKa and
therefore a larger Ka. This inverse logarithmic relationship is fundamental to
comparing acid strengths. A strong acid like HCl has a very low (even negative)
pKa.
,3. The equilibrium constant for the dissolution of a sparingly soluble ionic compound is
called:
A. Ka — acid dissociation constant
B. Kb — base dissociation constant
C. Ksp — solubility product constant
D. Kw — ion product constant for water
CORRECT ANSWER C — Ksp — solubility product constant
RATIONALE Ksp is the solubility product constant — the equilibrium constant for the
dissolution of a sparingly soluble ionic solid into its constituent ions in aqueous
solution. For example, AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq), Ksp = [Ag⁺][Cl⁻]. Ka (A) is for
acid dissociation. Kb (B) is for base dissociation. Kw (D) is the ion product
constant of water (1.0×10⁻¹⁴ at 25°C).
4. For the reaction A ⇌ B, the forward equilibrium constant is K = 4.0. What is the equilibrium
constant for the reverse reaction B ⇌ A?
A. 4.0
B. −4.0
C. 0.25
D. 16.0
CORRECT ANSWER C — 0.25
RATIONALE The equilibrium constant for a reverse reaction is the reciprocal of the forward
equilibrium constant: K_reverse = 1/K_forward. K = 4.0, so K_reverse = 1/4.0 =
0.25. This relationship holds because the products of the forward reaction
become the reactants of the reverse reaction, inverting the equilibrium
expression.
, 5. Which of the following is NOT one of the seven common strong acids?
A. HCl — hydrochloric acid
B. HNO₃ — nitric acid
C. HF — hydrofluoric acid
D. H₂SO₄ — sulfuric acid
CORRECT ANSWER C — HF — hydrofluoric acid
RATIONALE The seven strong acids are HCl, HBr, HI, HClO₃, HClO₄, HNO₃, and H₂SO₄. HF
(hydrofluoric acid) is notably a weak acid despite being a halogen acid — it only
partially ionizes in water due to the strong H–F bond. This is a common
misconception. All other options listed (HCl, HNO₃, H₂SO₄) are strong acids that
dissociate completely.
6. Le Chatelier's principle states that when stress is applied to a system at equilibrium, the
system will shift to relieve that stress. Which of the following are examples of such
stressors?
A. Concentration, temperature, pressure, and presence of a catalyst
B. Only concentration changes
C. Only temperature changes
D. Only pressure changes for gas reactions
CORRECT ANSWER A — Concentration, temperature, pressure, and presence of a catalyst
RATIONALE Stressors that can disturb a system at equilibrium include changes in
concentration (adding or removing reactants/products), temperature (exothermic
vs endothermic shifts), pressure (for gaseous systems with unequal moles of gas),
and the presence of a catalyst. Note: a catalyst speeds up the rate of reaching
equilibrium but does NOT shift the equilibrium position — it affects kinetics, not
thermodynamics.
