Chemistry 12 — U3 Practice Exam MCQ¶

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创建日期: 2026-03-14 最后更新: 2026-03-16

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题目数量：15 道选择题（Multiple Choice Questions）
来源：StudyForge — Quiz 11425-152507 (U3 Practice Exam)
答案位置：每题下方附 Answer
覆盖范围：Unit 3 — Chemical Equilibrium

Q1. In which of the following does the entropy decrease?

(A) NaCl(s) → Na⁺(aq) + Cl⁻(aq) (B) CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l) (C) 2NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g) (D) 4NO(g) + 6H₂O(g) → 4NH₃(g) + 5O₂(g)

Answer: (D)

Q2. Consider the following equilibrium:
COCl₂(g) ⇌ CO(g) + Cl₂(g) Keq = 8.1 × 10⁻⁴
For the above system,

(A) [COCl₂] < [CO][Cl₂] (B) [COCl₂] = 1 / ([CO][Cl₂]) (C) [COCl₂] = [CO][Cl₂] (D) [COCl₂] > [CO][Cl₂]

Answer: (D)

Q3. Consider the following reaction:
2C(s) + O₂(g) ⇌ 2CO(g)
A 1.00 L flask is initially filled with 2.00 mol C and 0.500 mol O₂. At equilibrium, the [O₂] is 0.250 mol/L. The Keq value is?

(A) 1.00 (B) 2.00 (C) 0.444 (D) 2.25

Answer: (A)

Q4. Consider the following:
2NO₂(g) ⇌ N₂O₄(g) Keq = 1.20
A 1.0 L flask is filled with 1.4 mol NO₂ and 2.0 mol N₂O₄. To reach equilibrium, the reaction proceeds to the?

(A) left as Trial Keq < Keq (B) left as Trial Keq > Keq (C) right as Trial Keq < Keq (D) right as Trial Keq > Keq

Answer: (C)

Q5. In an exothermic equilibrium reaction involving only gases, the value of Keq can be decreased by

(A) decreasing the temperature. (B) removing some reactant gas. (C) increasing the temperature. (D) adding some reactant gas.

Answer: (C)

Q6. Consider the following equilibrium:
I₂(s) + H₂O(l) ⇌ H⁺(aq) + I⁻(aq) + HOI(aq)
The equilibrium constant expression for the above system is

(A) Keq = [H⁺][I⁻][HOI] / [H₂O] (B) Keq = [H⁺][I⁻][HOI] / ([I₂][H₂O]) (C) Keq = [H⁺][I⁻][HOI] (D) Keq = [H⁺][I⁻]

Answer: (C)

Q7. Consider the following equilibrium:
2NO(g) + Cl₂(g) ⇌ 2NOCl(g) Keq = 12
At equilibrium, [NOCl] = 1.60 mol/L and [NO] = 0.80 mol/L. The [Cl₂] is?

(A) 3.0 mol/L (B) 0.17 mol/L (C) 0.27 mol/L (D) 0.33 mol/L

Answer: (D)

Q8. Consider the following equilibrium:
H₂(g) + CO₂(g) ⇌ CO(g) + H₂O(g) ΔH = +41 kJ
The temperature of the above equilibrium system is increased while kept at a constant volume. A new state of equilibrium is established in which there is

(A) an increase in [CO₂] and a decrease in Keq (B) an increase in [CO₂] and an increase in Keq (C) an increase in [CO] and an increase in Keq (D) an increase in [CO] and a decrease in Keq

Answer: (C)

Q9. Consider the following equilibrium:
2SO₃(g) ⇌ 2SO₂(g) + O₂(g)
The volume of the system is decreased at a constant temperature. A new state of equilibrium is established by a shift of the original equilibrium to the

(A) right and [SO₃] decreases. (B) left and [SO₃] increases. (C) left and [SO₃] remains unchanged. (D) right and [SO₃] remains unchanged.

Answer: (B)

Q10. Consider the following equilibrium:
2H₂S(g) ⇌ 2H₂(g) + S₂(g)
At equilibrium, [H₂S] = 0.50 mol/L, [H₂] = 0.10 mol/L and [S₂] = 0.40 mol/L. The value of Keq is calculated using the ratio?

(A) [0.10]²[0.40] / [0.50]² (B) [0.10][0.40] / [0.50] (C) [0.50]² / ([0.10]²[0.40]) (D) [0.50] / ([0.10][0.40])

Answer: (A)

Q11. Consider the following equilibrium:
SO₂Cl₂(g) ⇌ SO₂(g) + Cl₂(g)
A 1.0 L container is initially filled with 2.0 mol of SO₂Cl₂. As the reaction proceeds towards equilibrium, the rate of the forward reaction:

(A) increases and the [SO₂] decreases. (B) decreases and the [SO₂] increases. (C) increases and the [SO₂] increases. (D) decreases and the [SO₂] decreases.

Answer: (B)

Q12. Which of the following is true for all equilibrium systems?

(A) Addition of a catalyst changes the equilibrium concentrations. (B) The concentration of reactants is equal to the concentration of products. (C) The mass of reactants is equal to the mass of products. (D) The rate of the forward reaction is equal to the rate of the reverse reaction.

Answer: (D)

Q13. When the temperature of an equilibrium system is increased, the equilibrium always shifts to favour the

(A) endothermic reaction. (B) formation of products. (C) exothermic reaction. (D) formation of reactants.

Answer: (A)

Q14. Consider the following equilibrium:
2NO(g) + Cl₂(g) ⇌ 2NOCl(g)
At constant temperature and volume, Cl₂ is added to the above equilibrium system. As equilibrium reestablishes, the

(A) [NO] will increase. (B) [NOCl] will increase. (C) Keq will increase. (D) Keq will decrease.

Answer: (B)

Q15. Consider the following equilibrium:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) + 92 kJ
In which of the following will both changes shift the equilibrium right?

(A) A decrease in volume and an increase in temperature. (B) A decrease in volume and a decrease in temperature. (C) An increase in volume and a decrease in temperature. (D) An increase in volume and an increase in temperature.

Answer: (B)