The position of equilibrium
2 marks · NormalA reversible reaction occurs in a sealed container: . The forward reaction is exothermic.
State what happens to the position of equilibrium if:
the temperature is increased.
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.
Show answer
(a) The position of equilibrium shifts to the left (towards X/gas with fewer moles) when temperature is increased for an exothermic reaction.
(b) The equilibrium shifts to the left (towards X) when pressure is increased because there are fewer gas moles on the left.
Common mistakes: Stating concentrations are equal at equilibrium; Incorrect direction for pressure or temperature change
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States equilibrium shifts to the left (towards X) when temperature is increased for an exothermic reaction. Accept: 'towards reactants' or equivalent.
B2 (b) · 1 mark · States equilibrium shifts to the left (towards X) when pressure is increased because there are fewer gas molecules on that side. Accept: 'towards side with fewer moles'.
Worked solution
a) For an exothermic reaction, increasing the temperature shifts equilibrium to the left (towards reactants) to absorb the change.
b) Increasing the pressure favours the side with fewer moles of gas, shifting equilibrium to the left (towards X).