The position of equilibrium
2 marks · HardThe equilibrium below is set up in a sealed container: \[ \ce{2X(g) <=> Y(g) + 2Z(g)} \] The forward reaction is exothermic. State and explain what will happen to the position of equilibrium if the temperature is increased.
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The position of equilibrium shifts to the left (towards the reactants) because increasing temperature favours the endothermic (reverse) reaction.
Must show: States that equilibrium shifts to left/towards reactants, Explains that the reverse reaction is endothermic and is favoured
Also accept: Shifts in favour of reactants; Shifts to decrease temperature/endothermic direction
Common mistakes: Saying concentrations become equal; Forgetting to mention endothermic direction
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States that equilibrium shifts to the left/towards reactants or reverse reaction.
B2 · 1 mark · Explains that this is because increasing temperature favours the endothermic reaction (reverse reaction).
Worked solution
Increasing the temperature favours the endothermic direction of the reaction.
Here, the reverse reaction (right to left) is endothermic, so the position of equilibrium moves to the left, towards the reactants.