ORGANIC CHEMISTRY
CHM 202: GENERAL CHEMISTRY II
QUESTIONS AND ANSWERS
Chemical Equilibrium
1. At equilibrium, which of the following is true?
A. The rate of the forward reaction equals the rate of the reverse reaction.
B. The concentrations of reactants and products are equal.
C. The reaction has stopped.
D. The equilibrium constant is zero.
Correct Answer: A
Rationale: At equilibrium, the forward and reverse reaction rates are equal, so while the
concentrations remain constant, they are not necessarily equal.
2. For the general reaction aA + bB ⇌ cC + dD, the equilibrium constant expression,
K₍c₎, is given by:
A. K₍c₎ = [A]ᵃ[B]ᵇ⁄[C]ᶜ[D]ᵈ
B. K₍c₎ = [C]ᶜ[D]ᵈ⁄[A]ᵃ[B]ᵇ
C. K₍c₎ = ([C] + [D])⁽ᶜ⁺ᵈ⁾⁄([A] + [B])⁽ᵃ⁺ᵇ⁾
D. K₍c₎ = [C]⁄[A]
Correct Answer: B
Rationale: The equilibrium constant is defined as the product of the concentrations of the
products (each raised to its coefficient) divided by the product of the concentrations of
the reactants (each raised to its coefficient).
3. For a gaseous reaction, the relationship between K₍p₎ and K₍c₎ is given by:
A. K₍p₎ = K₍c₎(RT)^(Δn)
B. K₍p₎ = K₍c₎⁄(RT)^(Δn)
C. K₍p₎ = K₍c₎·(RT)^(–Δn)
D. K₍p₎ = K₍c₎(RT)^(–Δn)
Correct Answer: A
Rationale: For gaseous equilibria, K₍p₎ = K₍c₎(RT)^(Δn), where Δn = (moles of gaseous
products) – (moles of gaseous reactants).
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4. According to Le Chatelier’s Principle, if the concentration of a reactant is increased,
the equilibrium will shift:
A. Toward the reactants.
B. Toward the products.
C. It will not shift.
D. So as to decrease the equilibrium constant.
Correct Answer: B
Rationale: The system shifts in the direction that consumes the added reactant—in this
case, toward the products—to re-establish equilibrium.
5. For an exothermic reaction at equilibrium, an increase in temperature will cause the
equilibrium to shift:
A. Toward the products.
B. Toward the reactants.
C. No change; only the rate is affected.
D. To increase the value of K.
Correct Answer: B
Rationale: In an exothermic reaction, heat can be considered a product; increasing
temperature adds heat, shifting the equilibrium to favor the reactants.
6. The reaction quotient, Q, is used to:
A. Calculate the equilibrium constant.
B. Predict the direction in which a reaction will proceed to reach equilibrium.
C. Determine the rate of the reaction.
D. Measure the activation energy.
Correct Answer: B
Rationale: By comparing Q to K, one can predict whether the system will shift to
produce more products or reactants to reach equilibrium.
7. For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), Δn (moles of gas products minus
reactants) is:
A. –2
B. 2
C. –1
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D. 1
Correct Answer: A
Rationale: Total moles of gas on the reactant side = 1 + 3 = 4; on the product side = 2.
Thus, Δn = 2 – 4 = –2.
8. In a heterogeneous equilibrium, which species are omitted from the equilibrium
expression?
A. Gases
B. Aqueous ions
C. Pure solids and pure liquids
D. All species are included
Correct Answer: C
Rationale: Pure solids and liquids have constant concentrations and are not included in
the equilibrium constant expression.
9. For the equilibrium 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), if the pressure is increased by
decreasing the volume, the equilibrium shifts to:
A. The right (toward SO₃).
B. The left (toward SO₂ and O₂).
C. No shift occurs.
D. Increase the value of K.
Correct Answer: A
Rationale: Increasing pressure favors the side with fewer moles of gas. Here, reactants
total 3 moles while products total 2 moles.
10. Which of the following does NOT affect the position of equilibrium?
A. Changing concentrations.
B. Changing temperature.
C. Changing pressure (for gaseous systems).
D. Adding a catalyst.
Correct Answer: D
Rationale: A catalyst speeds up the attainment of equilibrium without affecting the
equilibrium position.
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CHM 202: GENERAL CHEMISTRY II
QUESTIONS AND ANSWERS
Chemical Equilibrium
1. At equilibrium, which of the following is true?
A. The rate of the forward reaction equals the rate of the reverse reaction.
B. The concentrations of reactants and products are equal.
C. The reaction has stopped.
D. The equilibrium constant is zero.
Correct Answer: A
Rationale: At equilibrium, the forward and reverse reaction rates are equal, so while the
concentrations remain constant, they are not necessarily equal.
2. For the general reaction aA + bB ⇌ cC + dD, the equilibrium constant expression,
K₍c₎, is given by:
A. K₍c₎ = [A]ᵃ[B]ᵇ⁄[C]ᶜ[D]ᵈ
B. K₍c₎ = [C]ᶜ[D]ᵈ⁄[A]ᵃ[B]ᵇ
C. K₍c₎ = ([C] + [D])⁽ᶜ⁺ᵈ⁾⁄([A] + [B])⁽ᵃ⁺ᵇ⁾
D. K₍c₎ = [C]⁄[A]
Correct Answer: B
Rationale: The equilibrium constant is defined as the product of the concentrations of the
products (each raised to its coefficient) divided by the product of the concentrations of
the reactants (each raised to its coefficient).
3. For a gaseous reaction, the relationship between K₍p₎ and K₍c₎ is given by:
A. K₍p₎ = K₍c₎(RT)^(Δn)
B. K₍p₎ = K₍c₎⁄(RT)^(Δn)
C. K₍p₎ = K₍c₎·(RT)^(–Δn)
D. K₍p₎ = K₍c₎(RT)^(–Δn)
Correct Answer: A
Rationale: For gaseous equilibria, K₍p₎ = K₍c₎(RT)^(Δn), where Δn = (moles of gaseous
products) – (moles of gaseous reactants).
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4. According to Le Chatelier’s Principle, if the concentration of a reactant is increased,
the equilibrium will shift:
A. Toward the reactants.
B. Toward the products.
C. It will not shift.
D. So as to decrease the equilibrium constant.
Correct Answer: B
Rationale: The system shifts in the direction that consumes the added reactant—in this
case, toward the products—to re-establish equilibrium.
5. For an exothermic reaction at equilibrium, an increase in temperature will cause the
equilibrium to shift:
A. Toward the products.
B. Toward the reactants.
C. No change; only the rate is affected.
D. To increase the value of K.
Correct Answer: B
Rationale: In an exothermic reaction, heat can be considered a product; increasing
temperature adds heat, shifting the equilibrium to favor the reactants.
6. The reaction quotient, Q, is used to:
A. Calculate the equilibrium constant.
B. Predict the direction in which a reaction will proceed to reach equilibrium.
C. Determine the rate of the reaction.
D. Measure the activation energy.
Correct Answer: B
Rationale: By comparing Q to K, one can predict whether the system will shift to
produce more products or reactants to reach equilibrium.
7. For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), Δn (moles of gas products minus
reactants) is:
A. –2
B. 2
C. –1
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D. 1
Correct Answer: A
Rationale: Total moles of gas on the reactant side = 1 + 3 = 4; on the product side = 2.
Thus, Δn = 2 – 4 = –2.
8. In a heterogeneous equilibrium, which species are omitted from the equilibrium
expression?
A. Gases
B. Aqueous ions
C. Pure solids and pure liquids
D. All species are included
Correct Answer: C
Rationale: Pure solids and liquids have constant concentrations and are not included in
the equilibrium constant expression.
9. For the equilibrium 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), if the pressure is increased by
decreasing the volume, the equilibrium shifts to:
A. The right (toward SO₃).
B. The left (toward SO₂ and O₂).
C. No shift occurs.
D. Increase the value of K.
Correct Answer: A
Rationale: Increasing pressure favors the side with fewer moles of gas. Here, reactants
total 3 moles while products total 2 moles.
10. Which of the following does NOT affect the position of equilibrium?
A. Changing concentrations.
B. Changing temperature.
C. Changing pressure (for gaseous systems).
D. Adding a catalyst.
Correct Answer: D
Rationale: A catalyst speeds up the attainment of equilibrium without affecting the
equilibrium position.
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