VCE-CHEM-U34 8.1 📋 Practice Exam 5: Question Paper

Write the Kc expression for: 2NO(g) + O₂(g) ⇌ 2NO₂(g). At equilibrium: [NO]=0.010, [O₂]=0.020, [NO₂]=0.080 mol/L. Calculate Kc.

A 1.0 L vessel initially contains 2.0 mol H₂ and 1.0 mol I₂. At equilibrium 1.6 mol HI has formed. Calculate Kc for H₂ + I₂ ⇌ 2HI.

Explain, using Le Chatelier’s principle, how three different changes affect the equilibrium position of:
PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) ΔH = +88 kJ

For the esterification equilibrium: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O, Kc = 4.0 at a given temperature.
If 1.0 mol each of acid and alcohol are mixed in 1.0 L, calculate equilibrium concentrations.

The industrial production of ammonia uses an iron catalyst at 450°C and 200 atm. Explain why the temperature used (450°C) is a compromise, given that the forward reaction is exothermic.

Ksp for BaSO₄ at 25°C = 1.1×10⁻¹⁰. Calculate (i) the molar solubility and (ii) whether a precipitate forms when 100 mL of 2×10⁻⁵ mol/L BaCl₂ is mixed with 100 mL of 2×10⁻⁵ mol/L Na₂SO₄.

Explain the relationship between Kc and Kp and derive the equation Kp = Kc(RT)^Δn.

A reaction mixture at equilibrium has Kc = 25. If the concentration of reactant A is 0.1 mol/L and product B is 0.5 mol/L for A ⇌ B:
(i) Verify equilibrium (ii) If [B] is suddenly doubled, find the new equilibrium concentrations.

Extended Response 1: Equilibrium Calculations

Extended Response 1: Equilibrium Calculations (a)
For the reaction CO(g) + 3H₂(g) ⇌ CH₄(g) + H₂O(g), Kc = 3.92 at 1000 K.
A mixture has [CO]=0.500, [H₂]=0.800, [CH₄]=0.300, [H₂O]=0.300 mol/L.
Calculate Q and determine the direction the reaction will proceed.

Extended Response 1: Equilibrium Calculations

Extended Response 1: Equilibrium Calculations (b)
Explain how the industrial synthesis of methane (methanation) would be optimised using Le Chatelier’s principle for the reaction CO(g) + 3H₂(g) ⇌ CH₄(g) + H₂O(g) ΔH = −206 kJ.

Extended Response 1: Equilibrium Calculations

Extended Response 1: Equilibrium Calculations (c)
Define the term ‘dynamic equilibrium’ and explain why it differs from a static equilibrium.

Extended Response 2: Ksp & Solubility

Extended Response 2: Ksp & Solubility (a)
The molar solubility of Ag₂CrO₄ is 6.5×10⁻⁵ mol/L at 25°C. Calculate Ksp.
(Ag₂CrO₄ ⇌ 2Ag⁺ + CrO₄²⁻)

Extended Response 2: Ksp & Solubility

Extended Response 2: Ksp & Solubility (b)
Explain the common ion effect. How does it affect the solubility of BaSO₄ if dissolved in 0.10 mol/L Na₂SO₄ instead of pure water?