25-minute Test : Part X Chemical Equilibrium

Consider the reversible reaction as shown. Which of the following statements concerning this reaction are correct if its temperature is increased at constant pressure?

(1) The mixture turns darker in colour.

(2) The rate of the backward reaction increases.

(3) There is an increase in the average molecular mass of gases.

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

Consider the reversible reaction as shown. At equilibrium, the reaction mixture is found to contain 0.00650 mol of N₂, 0.00350 mol of Cl₂ and 0.850 mol of NCl₃. What is the volume of the container?

• A. 1.07 dm³
• B. 1.15 dm³
• C. 1.32 dm³
• D. 1.74 dm³

The effects of temperature and pressure on the percentage yield of a reversible reaction are depicted as shown in the graph. Which of the following is likely to be the reversible reaction?

• A. N₂(g) + 3H₂(g) ⇌ 2NH₃(g)　　ΔH < 0

• B. P₄O₁₀(g) + 6PCl₅(g) ⇌ 10POCl₃(g)　　ΔH < 0

• C. 3O₂(g) ⇌ 2O₃(g)　　ΔH > 0

• D. CH₄(g) + H₂O(g) ⇌ CO(g) + 3H₂(g)　　ΔH > 0

Consider the equilibrium system established in a solution. Which of the following statements concerning the system is INCORRECT?

• A. The concentration of CrO₄²⁻(aq) is twice that of Cr₂O₇²⁻(aq) in the solution.
• B. On adding KOH(aq), the solution turns yellow.
• C. On adding H₂SO₄(aq), the equilibrium position shifts to the left.
• D. When the solution is cooled, its colour turns orange.

Consider the following reversible reaction at 300 K:

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)　　ΔH = −92 kJ mol⁻¹

Given that the equilibrium constant for this reaction is 2.7 × 10⁸ mol⁻² dm⁶ at 300 K, which of the statements is/are correct?

• A. (1) only
• B. (2) only
• C. (1) and (3) only
• D. (2) and (3) only

Refer to the information in the diagram. What is the equilibrium constant for the following reaction?

P(aq) + S(aq) ⇌ T(aq)

• A
• B
• C
• D

Fe³⁺(aq) reacts with SCN⁻(aq) reversibly to form Fe(SCN)²⁺(aq). An equilibrium mixture is prepared by mixing 20.0 cm³ of 0.030 M Fe(NO₃)₃(aq) with 10.0 cm³ of 0.030 M KSCN(aq). What is the concentration of Fe(SCN)²⁺(aq) in the equilibrium mixture?

• A. 2.17 × 10⁻³ mol dm⁻³
• B. 4.62 × 10⁻³ mol dm⁻³
• C. 9.21 × 10⁻³ mol dm⁻³
• D. 1.842 × 10⁻² mol dm⁻³

P(g) and Q(g) react reversibly to give R(g) in a fixed-volume closed container maintained at a constant temperature. The graph below shows the changes in concentrations of P(g), Q(g) and R(g) over time. Which of the options is the equilibrium constant expression for the reaction?

• A
• B
• C
• D

The chemical equilibrium as shown has been established in a fixed-volume closed reaction vessel at a certain temperature.

• A
• B
• C
• D

Consider the ionization of water:

H₂O(l) ⇌ H⁺(aq) + OH⁻(aq)　　ΔH > 0

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)