CHEM 104 Final Exam | General Chemistry II w/Lab
Exam Q&A | Portage Learning
1. Which of the following statements best describes the relationship between the
equilibrium constant (K) and the standard Gibbs free energy change (ΔG°) for a
reaction?
A) A negative ΔG° corresponds to a K value less than 1.
B) A positive ΔG° corresponds to a K value greater than 1.
C) A negative ΔG° corresponds to a K value greater than 1.
D) ΔG° and K are not related to each other.
Correct Answer: A negative ΔG° corresponds to a K value greater than 1.
Rationale: The relationship between standard free energy and the equilibrium constant
is given by ΔG° = -RT ln K. When ΔG° is negative, ln K must be positive, meaning K > 1,
indicating that products are favored at equilibrium. When ΔG° is positive, K < 1 and
reactants are favored. The other options misstate this thermodynamic relationship.
2. What is the primary function of a buffer solution in a chemical or biological
system?
A) To increase the pH of a solution dramatically.
B) To resist changes in pH upon addition of small amounts of acid or base.
C) To completely neutralize any added acid or base.
D) To catalyze biochemical reactions.
Correct Answer: To resist changes in pH upon addition of small amounts of acid or base.
Rationale: A buffer is a solution containing a weak acid and its conjugate base (or a weak
base and its conjugate acid) that resists significant pH changes when small quantities of
strong acid or base are added. It does not completely neutralize added acid or base, nor
does it catalyze reactions or dramatically increase pH. This property is crucial in
biological systems and laboratory experiments.
3. According to collision theory, which factor is most important in determining
whether a reaction will occur when two molecules collide?
A) The color of the molecules involved.
B) The activation energy of the reaction.
C) The volume of the reaction container.
D) The mass of the container.
Correct Answer: The activation energy of the reaction.
Rationale: Collision theory states that for a reaction to occur, colliding molecules must
possess sufficient kinetic energy to overcome the activation energy barrier and must
collide with the proper orientation. The activation energy is the minimum energy
,required for a successful reaction. Color, container volume, and container mass do not
directly determine whether a molecular collision leads to a reaction.
4. A researcher is studying a first-order reaction and observes that the half-life is
20.0 minutes. What is the rate constant (k) for this reaction?
A) 0.0347 min⁻¹
B) 0.693 min⁻¹
C) 0.0200 min⁻¹
D) 13.9 min⁻¹
Correct Answer: 0.0347 min⁻¹
Rationale: For a first-order reaction, the half-life is related to the rate constant by the
equation t₁/₂ = 0.693 / k. Rearranging gives k = 0.693 / t₁/₂ = 0..0 min = 0.0347
min⁻¹. Option B is the value of 0.693, option C is the reciprocal of the half-life, and
option D is the reciprocal of the rate constant.
5. Which term refers to the minimum energy that colliding molecules must possess
for a reaction to occur?
A) Enthalpy
B) Entropy
C) Activation energy
D) Free energy
Correct Answer: Activation energy
Rationale: Activation energy (Ea) is the minimum energy that reactant molecules must
have for a collision to result in a chemical reaction. Enthalpy (H) is the heat content of a
system, entropy (S) is a measure of disorder, and free energy (G) determines
spontaneity. Only activation energy specifically describes the energy barrier for a
reaction.
6. What is the correct expression for the equilibrium constant (Kc) for the reaction:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)?
A) Kc = [SO₃]² / ([SO₂]²[O₂])
B) Kc = ([SO₂]²[O₂]) / [SO₃]²
C) Kc = [SO₃] / ([SO₂][O₂])
D) Kc = ([SO₂][O₂]) / [SO₃]
Correct Answer: Kc = [SO₃]² / ([SO₂]²[O₂])
Rationale: The equilibrium constant expression is the product of the concentrations of
the products raised to their stoichiometric coefficients divided by the product of the
concentrations of the reactants raised to their stoichiometric coefficients. For this
reaction: Kc = [SO₃]² / ([SO₂]²[O₂]). The other options have incorrect exponents or are
inverted.
, 7. Which principle explains why the addition of a common ion decreases the
solubility of a slightly soluble salt?
A) Le Chatelier's principle
B) Hund's rule
C) Aufbau principle
D) Heisenberg uncertainty principle
Correct Answer: Le Chatelier's principle
Rationale: The common ion effect is a direct application of Le Chatelier's principle.
When a common ion is added to a saturated solution of a slightly soluble salt, the
equilibrium shifts to the left to relieve the stress, causing more solid to precipitate and
decreasing solubility. Hund's rule, the Aufbau principle, and the Heisenberg uncertainty
principle are unrelated to solubility equilibria.
8. The nurse is reviewing a patient's arterial blood gas results and notes a pH of
7.30. Which condition does this value indicate?
A) Acidosis
B) Alkalosis
C) Normal pH
D) Neutral pH
Correct Answer: Acidosis
Rationale: Normal arterial blood pH is tightly regulated between 7.35 and 7.45. A pH of
7.30 is below this range and indicates acidosis. Alkalosis would be indicated by a pH
above 7.45. A neutral pH of 7.00 is not compatible with life, and "normal pH" would fall
within the 7.35–7.45 range.
9. What is the molecular geometry of a molecule with the VSEPR formula AX₄E₂?
A) Tetrahedral
B) Square planar
C) Octahedral
D) Bent
Correct Answer: Square planar
Rationale: The VSEPR formula AX₄E₂ indicates four bonding pairs and two lone pairs on
the central atom. The electron geometry is octahedral, but the molecular geometry
(considering only atoms) is square planar, as seen in XeF₄. Tetrahedral would be AX₄,
octahedral would be AX₆, and bent would be AX₂E₂.
10. Which of the following is a strong acid?
A) HF
B) CH₃COOH
Exam Q&A | Portage Learning
1. Which of the following statements best describes the relationship between the
equilibrium constant (K) and the standard Gibbs free energy change (ΔG°) for a
reaction?
A) A negative ΔG° corresponds to a K value less than 1.
B) A positive ΔG° corresponds to a K value greater than 1.
C) A negative ΔG° corresponds to a K value greater than 1.
D) ΔG° and K are not related to each other.
Correct Answer: A negative ΔG° corresponds to a K value greater than 1.
Rationale: The relationship between standard free energy and the equilibrium constant
is given by ΔG° = -RT ln K. When ΔG° is negative, ln K must be positive, meaning K > 1,
indicating that products are favored at equilibrium. When ΔG° is positive, K < 1 and
reactants are favored. The other options misstate this thermodynamic relationship.
2. What is the primary function of a buffer solution in a chemical or biological
system?
A) To increase the pH of a solution dramatically.
B) To resist changes in pH upon addition of small amounts of acid or base.
C) To completely neutralize any added acid or base.
D) To catalyze biochemical reactions.
Correct Answer: To resist changes in pH upon addition of small amounts of acid or base.
Rationale: A buffer is a solution containing a weak acid and its conjugate base (or a weak
base and its conjugate acid) that resists significant pH changes when small quantities of
strong acid or base are added. It does not completely neutralize added acid or base, nor
does it catalyze reactions or dramatically increase pH. This property is crucial in
biological systems and laboratory experiments.
3. According to collision theory, which factor is most important in determining
whether a reaction will occur when two molecules collide?
A) The color of the molecules involved.
B) The activation energy of the reaction.
C) The volume of the reaction container.
D) The mass of the container.
Correct Answer: The activation energy of the reaction.
Rationale: Collision theory states that for a reaction to occur, colliding molecules must
possess sufficient kinetic energy to overcome the activation energy barrier and must
collide with the proper orientation. The activation energy is the minimum energy
,required for a successful reaction. Color, container volume, and container mass do not
directly determine whether a molecular collision leads to a reaction.
4. A researcher is studying a first-order reaction and observes that the half-life is
20.0 minutes. What is the rate constant (k) for this reaction?
A) 0.0347 min⁻¹
B) 0.693 min⁻¹
C) 0.0200 min⁻¹
D) 13.9 min⁻¹
Correct Answer: 0.0347 min⁻¹
Rationale: For a first-order reaction, the half-life is related to the rate constant by the
equation t₁/₂ = 0.693 / k. Rearranging gives k = 0.693 / t₁/₂ = 0..0 min = 0.0347
min⁻¹. Option B is the value of 0.693, option C is the reciprocal of the half-life, and
option D is the reciprocal of the rate constant.
5. Which term refers to the minimum energy that colliding molecules must possess
for a reaction to occur?
A) Enthalpy
B) Entropy
C) Activation energy
D) Free energy
Correct Answer: Activation energy
Rationale: Activation energy (Ea) is the minimum energy that reactant molecules must
have for a collision to result in a chemical reaction. Enthalpy (H) is the heat content of a
system, entropy (S) is a measure of disorder, and free energy (G) determines
spontaneity. Only activation energy specifically describes the energy barrier for a
reaction.
6. What is the correct expression for the equilibrium constant (Kc) for the reaction:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)?
A) Kc = [SO₃]² / ([SO₂]²[O₂])
B) Kc = ([SO₂]²[O₂]) / [SO₃]²
C) Kc = [SO₃] / ([SO₂][O₂])
D) Kc = ([SO₂][O₂]) / [SO₃]
Correct Answer: Kc = [SO₃]² / ([SO₂]²[O₂])
Rationale: The equilibrium constant expression is the product of the concentrations of
the products raised to their stoichiometric coefficients divided by the product of the
concentrations of the reactants raised to their stoichiometric coefficients. For this
reaction: Kc = [SO₃]² / ([SO₂]²[O₂]). The other options have incorrect exponents or are
inverted.
, 7. Which principle explains why the addition of a common ion decreases the
solubility of a slightly soluble salt?
A) Le Chatelier's principle
B) Hund's rule
C) Aufbau principle
D) Heisenberg uncertainty principle
Correct Answer: Le Chatelier's principle
Rationale: The common ion effect is a direct application of Le Chatelier's principle.
When a common ion is added to a saturated solution of a slightly soluble salt, the
equilibrium shifts to the left to relieve the stress, causing more solid to precipitate and
decreasing solubility. Hund's rule, the Aufbau principle, and the Heisenberg uncertainty
principle are unrelated to solubility equilibria.
8. The nurse is reviewing a patient's arterial blood gas results and notes a pH of
7.30. Which condition does this value indicate?
A) Acidosis
B) Alkalosis
C) Normal pH
D) Neutral pH
Correct Answer: Acidosis
Rationale: Normal arterial blood pH is tightly regulated between 7.35 and 7.45. A pH of
7.30 is below this range and indicates acidosis. Alkalosis would be indicated by a pH
above 7.45. A neutral pH of 7.00 is not compatible with life, and "normal pH" would fall
within the 7.35–7.45 range.
9. What is the molecular geometry of a molecule with the VSEPR formula AX₄E₂?
A) Tetrahedral
B) Square planar
C) Octahedral
D) Bent
Correct Answer: Square planar
Rationale: The VSEPR formula AX₄E₂ indicates four bonding pairs and two lone pairs on
the central atom. The electron geometry is octahedral, but the molecular geometry
(considering only atoms) is square planar, as seen in XeF₄. Tetrahedral would be AX₄,
octahedral would be AX₆, and bent would be AX₂E₂.
10. Which of the following is a strong acid?
A) HF
B) CH₃COOH
