Question 1: Define dynamic equilibrium in the context of reversible chemical reactions.

Answer: Dynamic equilibrium occurs when the rate of the forward reaction equals the rate of the backward reaction in a reversible reaction, resulting in constant concentrations of reactants and products.

Question 2: Describe the mechanism that leads to a state of dynamic equilibrium in a closed system.

Answer: In a closed system, the forward and backward reactions occur simultaneously at equal rates, so the concentrations of reactants and products remain constant over time, maintaining a dynamic balance.

Question 1: For the reaction A ⇌ B, the initial concentration of A is 0.5 mol/L. At equilibrium, the concentration of B is 0.3 mol/L. Assuming no B initially, calculate the equilibrium concentration of A, given that the reaction is at equilibrium.

Answer: 0.2 mol/L

Question 2: Using the data: [A]initial = 1.0 mol/L, [A] at equilibrium = 0.6 mol/L, calculate the value of the equilibrium constant (Kc) for the reaction A ⇌ B, assuming B forms from A.

Answer: Kc = 0.67

Question 1: Outline a safe method to investigate the effect of temperature on the position of equilibrium in the Haber process.

Answer: Use a sealed reaction vessel, maintain consistent pressure, control temperature with a thermostat, wear safety goggles and gloves, and ensure proper ventilation. Record the equilibrium position at different temperatures.

Question 1: A reversible reaction reaches equilibrium with the following concentration data: at 25°C, [A] = 0.4 mol/L and [B] = 0.6 mol/L; at 50°C, [A] = 0.3 mol/L and [B] = 0.7 mol/L. Explain how temperature affects the position of equilibrium and the value of the equilibrium constant.

Answer: As temperature increases from 25°C to 50°C, the concentration of B increases while A decreases, indicating the equilibrium shifts to favour the formation of B. This suggests the forward reaction is endothermic. The value of Kc increases with temperature, confirming that higher temperature shifts the equilibrium position towards products in an endothermic reaction.

Question 1: Explain why the concentrations of reactants and products remain constant once equilibrium is established in a closed system. (3 marks)

Answer: Because the rates of the forward and backward reactions are equal, the net change in concentrations is zero, resulting in constant concentrations of reactants and products despite ongoing reactions.

Question 2: A reaction A + B ⇌ C + D has an equilibrium constant Kc = 4. If the initial concentrations are [A] = 1.0 mol/L, [B] = 1.0 mol/L, and initially no C or D, what will be the concentrations of C and D at equilibrium? (Assume x mol/L of A and B react to form C and D.)

Answer: At equilibrium: [A] = 1.0 - x, [B] = 1.0 - x, [C] = x, [D] = x. Using Kc = 4, (x)(x) / [(1 - x)(1 - x)] = 4. Solving yields x ≈ 0.66 mol/L. Therefore, [C] ≈ 0.66 mol/L, [D] ≈ 0.66 mol/L, and [A], [B] ≈ 0.34 mol/L.

Question 1: Explain how Le Châtelier's principle applies to the Haber process and why controlling temperature and pressure is important in industrial ammonia production.

Answer: Le Châtelier's principle states that a system at equilibrium will adjust to counter any changes. In the Haber process, increasing temperature shifts equilibrium to produce less ammonia (exothermic reaction), while increasing pressure favours ammonia formation. Controlling these conditions optimises yield and energy efficiency.