The position of equilibrium

2 marks · Easy

The reversible reaction below is in a sealed container at equilibrium:

There are equal numbers of moles of gas on both sides of the equation, and the forward reaction is endothermic.

Explain, with a reason, the effect on the position of equilibrium if the pressure is increased.

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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There is no effect on the position of equilibrium.

Also accept: Equilibrium position does not change; No change to the position of equilibrium

Common mistakes: Saying 'forward reaction favoured' or 'more product formed'; Claiming a shift occurs without stating reason about equal gas moles

Show mark scheme and worked solution

Marking points

M1 · 1 mark · States that increasing pressure has no effect on the position of equilibrium.

E1 · 1 mark · Gives a correct reason: the number of moles of gas is the same on both sides of the equation.

Worked solution

The equation shows one mole of gas reacting with one mole to give two moles of gas on the right.

Total moles of gas on left = 2; total on right = 2.

Changing the pressure does not affect the position of equilibrium because there is the same number of gas molecules on each side.