Changing the temperature
3 marks · NormalThe reaction below reaches equilibrium at a certain temperature:
Explain what will happen to the position of equilibrium if you decrease the temperature. Refer to the direction of the equilibrium shift.
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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Also accept: If the forward reaction is exothermic, decreasing temperature favours the formation of AB; the equilibrium shifts to the right.; If the forward reaction is endothermic, decreasing temperature favours the reverse.
Common mistakes: Omitting link between temperature and exothermic direction; Not stating which side is favoured
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Marking points
B1 · 1 mark · States that lowering temperature favours the exothermic direction.
M1 · 1 mark · States the equilibrium will shift towards more AB (if forward exothermic) or specifies the direction correctly.
M2 · 1 mark · Explains that this is because the system responds by producing more heat.
Worked solution
Decreasing the temperature favours the exothermic direction of the reaction.
If the forward reaction is exothermic, the equilibrium shifts to the right, producing more AB.
This is because the system produces more heat to raise the temperature again.