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An equilibrium mixture is prepared in a container of fixed volume - AQA - A-Level Chemistry - Question 20 - 2017 - Paper 3
Question 20
An equilibrium mixture is prepared in a container of fixed volume. CO(g) + Cl2(g) ⇌ COCl2(g) ΔH = -108 kJ mol⁻¹ The temperature of this mixture is decreased and t... show full transcript
Worked Solution & Example Answer:An equilibrium mixture is prepared in a container of fixed volume - AQA - A-Level Chemistry - Question 20 - 2017 - Paper 3
Step 1
Which is greater for the new equilibrium than for the original equilibrium?
Answer
To analyze the impact of decreasing the temperature on the equilibrium, we need to refer to Le Chatelier's principle, which states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
In this case, since the reaction is exothermic (ΔH = -108 kJ mol⁻¹), lowering the temperature will favor the forward reaction, which produces more COCl₂. This shift increases the concentration of the products relative to the reactants.
Therefore, the value of the equilibrium constant, Kc, which is temperature dependent, will also change. For an exothermic reaction, as the temperature decreases, the equilibrium constant, Kc, increases. Hence, the correct answer is:
D. The value of the equilibrium constant, Kc