This higher tier covers Le Chatelier's Principle (Higher Tier) within Equilibrium (HT) for GCSE Chemistry. Revise Equilibrium (HT) in Rates of Reaction for GCSE Chemistry with 23 exam-style questions and 18 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 14 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
🎓 Le Chatelier's Principle (Higher Tier)
"If a system at equilibrium is disturbed, it will shift in the direction that opposes the change."
Effect of changing CONDITIONS:
| Condition changed | Direction of shift | Why |
|---|---|---|
| Temperature ↑ | Shifts in the ENDOTHERMIC direction | System absorbs the extra heat |
| Temperature ↓ | Shifts in the EXOTHERMIC direction | System releases heat to compensate |
| Concentration of reactant ↑ | Shifts to PRODUCTS (right) | System uses up the added substance |
| Concentration of product ↑ | Shifts to REACTANTS (left) | System uses up the added substance |
| Pressure ↑ (gases only) | Shifts to side with FEWER gas molecules | System reduces the pressure |
| Pressure ↓ (gases only) | Shifts to side with MORE gas molecules | System increases the pressure |
What about catalysts? Catalysts do NOT change equilibrium position — they help reach equilibrium faster by speeding up BOTH forward and backward reactions equally.
Quick Check: A student adds a catalyst to a reversible reaction at equilibrium. Explain whether the position of equilibrium shifts.
The position of equilibrium does NOT shift. A catalyst speeds up both the forward AND the backward reactions equally, so the ratio of products to reactants at equilibrium remains the same. The system simply reaches equilibrium faster. This is an important distinction — catalysts increase the rate of reaching equilibrium, but do not change where equilibrium lies.
Practice questions for Equilibrium (HT)
At dynamic equilibrium, which of the following is true?
Explain the effect of increasing temperature on the position of an equilibrium where the forward reaction is exothermic.