CH
,EM 104 Module 2 Exam General Chemistry II
w/Lab | Portage | 26/27|Q&A Actual (PDF)
1. Which statement accurately characterizes a system that has reached chemical equilibrium?
A) The concentrations of reactants and products are equal.
B) The forward and reverse reaction rates are equal and constant.
C) The reaction has stopped completely.
D) The equilibrium constant must equal one.
Correct Answer: The forward and reverse reaction rates are equal and constant.
Rationale: At equilibrium, the rates of the forward and reverse reactions are equal, so concentrations
remain constant over time, though they are not necessarily equal. Option A is a common
misconception; equilibrium does not require equal concentrations. Option C is incorrect because
equilibrium is dynamic, and option D is incorrect because K can be any positive value.
2. What is the correct expression for the equilibrium constant Kc for the reaction N2(g) + 3 H2(g) ⇌ 2
NH3(g)?
A) Kc = [NH3]^2 / ([N2][H2]^3)
B) Kc = ([N2][H2]^3) / [NH3]^2
C) Kc = [NH3] / ([N2][H2])
D) Kc = [NH3]^2 / ([N2]^3[H2])
,Correct Answer: Kc = [NH3]^2 / ([N2][H2]^3)
Rationale: The equilibrium constant expression places product concentrations raised to their
stoichiometric coefficients in the numerator and reactant concentrations raised to their coefficients in
the denominator. Option B is the reciprocal, option C ignores stoichiometric coefficients, and option D
incorrectly applies the coefficient of N2 to H2.
3. For the reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g), what happens to the equilibrium position when the
volume of the container is decreased at constant temperature?
A) The equilibrium shifts toward the reactants.
B) The equilibrium shifts toward the products.
C) The equilibrium position does not change.
D) The equilibrium constant increases.
Correct Answer: The equilibrium shifts toward the products.
Rationale: Decreasing the volume increases the pressure, and by Le Chatelier's principle, the system
shifts toward the side with fewer moles of gas to relieve the stress. The reactant side has 3 moles of
gas while the product side has 2 moles, so the equilibrium shifts toward products. The equilibrium
constant remains unchanged by volume or pressure changes.
4. Which of the following is true about the reaction quotient Q when Q > K?
A) The reaction proceeds in the forward direction to reach equilibrium.
B) The reaction proceeds in the reverse direction to reach equilibrium.
, C) The system is at equilibrium.
D) The reaction has stopped.
Correct Answer: The reaction proceeds in the reverse direction to reach equilibrium.
Rationale: When Q > K, the ratio of products to reactants is greater than at equilibrium, meaning there
is an excess of products. The system will shift in the reverse direction, converting products into
reactants until Q equals K. Option A would be true if Q < K, and option C would be true if Q = K.
5. What is the correct expression for the solubility product constant Ksp of PbCl2?
A) Ksp = [Pb2+][Cl-]
B) Ksp = [Pb2+][Cl-]^2
C) Ksp = [Pb2+]^2[Cl-]
D) Ksp = [Pb2+][2Cl-]^2
Correct Answer: Ksp = [Pb2+][Cl-]^2
Rationale: The dissolution of PbCl2 is PbCl2(s) ⇌ Pb2+(aq) + 2 Cl-(aq). The Ksp expression is the
product of the ion concentrations, each raised to its stoichiometric coefficient: Ksp = [Pb2+][Cl-]^2.
Option D incorrectly uses 2 as a coefficient inside the concentration term, and options A and C have
incorrect exponents.
6. According to Le Chatelier's principle, what happens to the equilibrium of an exothermic reaction
when the temperature is increased?
,EM 104 Module 2 Exam General Chemistry II
w/Lab | Portage | 26/27|Q&A Actual (PDF)
1. Which statement accurately characterizes a system that has reached chemical equilibrium?
A) The concentrations of reactants and products are equal.
B) The forward and reverse reaction rates are equal and constant.
C) The reaction has stopped completely.
D) The equilibrium constant must equal one.
Correct Answer: The forward and reverse reaction rates are equal and constant.
Rationale: At equilibrium, the rates of the forward and reverse reactions are equal, so concentrations
remain constant over time, though they are not necessarily equal. Option A is a common
misconception; equilibrium does not require equal concentrations. Option C is incorrect because
equilibrium is dynamic, and option D is incorrect because K can be any positive value.
2. What is the correct expression for the equilibrium constant Kc for the reaction N2(g) + 3 H2(g) ⇌ 2
NH3(g)?
A) Kc = [NH3]^2 / ([N2][H2]^3)
B) Kc = ([N2][H2]^3) / [NH3]^2
C) Kc = [NH3] / ([N2][H2])
D) Kc = [NH3]^2 / ([N2]^3[H2])
,Correct Answer: Kc = [NH3]^2 / ([N2][H2]^3)
Rationale: The equilibrium constant expression places product concentrations raised to their
stoichiometric coefficients in the numerator and reactant concentrations raised to their coefficients in
the denominator. Option B is the reciprocal, option C ignores stoichiometric coefficients, and option D
incorrectly applies the coefficient of N2 to H2.
3. For the reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g), what happens to the equilibrium position when the
volume of the container is decreased at constant temperature?
A) The equilibrium shifts toward the reactants.
B) The equilibrium shifts toward the products.
C) The equilibrium position does not change.
D) The equilibrium constant increases.
Correct Answer: The equilibrium shifts toward the products.
Rationale: Decreasing the volume increases the pressure, and by Le Chatelier's principle, the system
shifts toward the side with fewer moles of gas to relieve the stress. The reactant side has 3 moles of
gas while the product side has 2 moles, so the equilibrium shifts toward products. The equilibrium
constant remains unchanged by volume or pressure changes.
4. Which of the following is true about the reaction quotient Q when Q > K?
A) The reaction proceeds in the forward direction to reach equilibrium.
B) The reaction proceeds in the reverse direction to reach equilibrium.
, C) The system is at equilibrium.
D) The reaction has stopped.
Correct Answer: The reaction proceeds in the reverse direction to reach equilibrium.
Rationale: When Q > K, the ratio of products to reactants is greater than at equilibrium, meaning there
is an excess of products. The system will shift in the reverse direction, converting products into
reactants until Q equals K. Option A would be true if Q < K, and option C would be true if Q = K.
5. What is the correct expression for the solubility product constant Ksp of PbCl2?
A) Ksp = [Pb2+][Cl-]
B) Ksp = [Pb2+][Cl-]^2
C) Ksp = [Pb2+]^2[Cl-]
D) Ksp = [Pb2+][2Cl-]^2
Correct Answer: Ksp = [Pb2+][Cl-]^2
Rationale: The dissolution of PbCl2 is PbCl2(s) ⇌ Pb2+(aq) + 2 Cl-(aq). The Ksp expression is the
product of the ion concentrations, each raised to its stoichiometric coefficient: Ksp = [Pb2+][Cl-]^2.
Option D incorrectly uses 2 as a coefficient inside the concentration term, and options A and C have
incorrect exponents.
6. According to Le Chatelier's principle, what happens to the equilibrium of an exothermic reaction
when the temperature is increased?
