AQA · Chemistry · 8462
GCSE Chemistry (AQA): Le Chatelier's Principle
Topic 6 — The Rate & Extent of Chemical Change. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Le Chatelier's Principle - Position of Equilibrium in Reversible Reactions"; each card deep-links to the moment in the video it came from. Lesson 6.07 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_6.07.
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What does a negative overall energy change (e.g. −92 kJ/mol) tell you about a forward reaction?
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It is exothermic — it releases energy to the surroundings.
Why does increasing pressure shift equilibrium to the side with fewer gas molecules?
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Pressure is a measure of particles per unit volume, so forming fewer molecules lowers the pressure and counteracts the increase.
Which direction does equilibrium shift when the temperature is increased?
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In the endothermic direction, absorbing heat energy to oppose the rise in temperature.
In the Haber process equilibrium, what happens to ammonia yield if the temperature is lowered?
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It increases — the forward reaction is exothermic, so equilibrium shifts right, giving more ammonia and less nitrogen and hydrogen.
What does Le Chatelier's principle state?
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If the conditions of a reversible reaction at equilibrium are changed, the position of equilibrium shifts to counteract that change.
If the forward reaction of a reversible reaction is exothermic, what is the backward reaction?
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Endothermic — the backward reaction is always the opposite of the forward reaction.
Increasing the pressure of a gaseous equilibrium shifts it to the side with ? molecules.
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fewer
Why does increasing pressure favour ammonia in N₂ + 3H₂ ⇌ 2NH₃?
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There are 4 molecules on the left but only 2 on the right, so shifting right reduces the number of gas molecules and the pressure.
Which direction does equilibrium shift when the temperature is decreased?
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In the exothermic direction, releasing heat energy to counteract the drop in temperature.
Which direction does a gaseous equilibrium shift when the pressure is decreased?
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To the side with more molecules, in order to increase the pressure again.
What does the 'position of equilibrium' describe?
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How many reactant particles there are compared with product particles at equilibrium — it lies to the left if there are more reactants, to the right if there are more products.
What happens to the position of equilibrium if the concentration of a reactant is increased?
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It shifts towards the products (the opposite side) to use up the added reactant.
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