Le Chatelier's principle
| English | Chinese | Pinyin |
|---|---|---|
| Le Chatelier's principle | 勒夏特列原理 | lēi xià tè liè yuán lǐ |
| equilibrium | 平衡 | píng héng |
| catalyst | 催化剂 | cuī huà jì |
| endothermic | 吸热 | xī rè |
Nudging a balance
- Le Chatelier's principle 勒夏特列原理: if you change a system at equilibrium 平衡, it shifts to oppose the change.
- This predicts which way the equilibrium moves.
- A catalyst 催化剂 is the exception — it shifts nothing.
Le Chatelier's principle says that a change to a system at equilibrium causes it to:
The equilibrium position always moves in the direction that lessens the change you made.
Increasing the pressure shifts equilibrium towards the side with fewer gas molecules.
Le Chatelier's principle.
The changes
| Change | Equilibrium moves |
|---|---|
| increase a reactant's concentration | towards products |
| increase pressure | towards the side with fewer gas molecules |
| increase temperature | towards the endothermic 吸热 direction |
Le Chatelier's principle: the equilibrium shifts to oppose the change you make
Le Chatelier's principle
the system opposes the change
Raise T, P or reactant and the equilibrium shifts to oppose your change.
Increasing the pressure shifts the equilibrium towards:
Moving to fewer gas molecules reduces the pressure, opposing the increase.
Increasing the temperature shifts the equilibrium towards:
The endothermic direction absorbs the added heat, opposing the temperature rise.
Catalysts
- A catalyst speeds up both the forward and reverse reactions equally.
- So equilibrium is reached faster, but its position does not change.
Adding a catalyst to a system at equilibrium:
A catalyst speeds up both directions equally, so the position of equilibrium is unchanged.
Match each change to how the equilibrium responds.
Each item links the term to its correct meaning.
Temperature and the catalyst
- Raising temperature shifts equilibrium in the endothermic direction.
- A catalyst speeds up both directions equally, so it does not shift the position.
You've got it
- Le Chatelier: the equilibrium shifts to oppose any change you make
- more reactant → towards products; more pressure → fewer-gas-molecules side; more heat → endothermic direction
- a catalyst speeds both ways equally → reaches equilibrium faster, no shift