The position of equilibrium
2 marks · EasyConsider the equilibrium reaction in a sealed container:
The forward reaction is exothermic. The system is at equilibrium at 400 K and 2 atm pressure.
Calculate the qualitative effect (increase, decrease or no change) on the amount of at equilibrium if:
(a) the temperature is decreased, but the pressure is kept constant.
State the effect on at equilibrium and explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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The amount of increases.
(a) Increases. Explanation: Lowering the temperature favors the exothermic (forward) reaction, so more is formed. · must show Correct prediction (increase), Reference to exothermic reaction and/or Le Chatelier's principle
Also accept: increases; more is formed; equilibrium shifts to the right/increased product
Common mistakes: Saying 'no change' or 'decreases'; Mixing up exothermic/endothermic
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · States that the amount of increases.
E1 (a) · 1 mark · States that decreasing temperature favours the exothermic forward reaction (or uses Le Chatelier's principle correctly).
Worked solution
The forward reaction is exothermic. According to Le Chatelier's principle, decreasing the temperature favours the exothermic direction.
So, the equilibrium shifts to the right and more is formed.
Therefore, the amount of at equilibrium increases.