# Equilibrium displacement

## Le Châtelier's law

### Influence of the temperature

If the weather is fine: The (tiring!) migration lowlands $\longrightarrow$ mountain is favoured. The equilibrium of the upward and downward migrations tends toward the mountain.

If it is raining: The (relaxing!) migration mountain $\longrightarrow$ lowlands is favoured. The equilibrium of the upward and downward migrations tends toward the lowlands.

Similarly, in chemistry:

Raising the temperature favours the endothermic reaction (which absorbs heat) Lowering the temperature favours the exothermic reaction (which produces heat)

### Influence of the concentrations

Our little paradise is not overcrowded: Some tourists make efforts in the mountain, others relax in the plain. The ratio tourists-mountain/ tourists-plain is about equal to 2. We have an equilibrium.

Alas, there are now new tourists landing in the plain, so that suddenly there are much more tourists in the plain than in the mountain! The equilibrium is disrupted.

Some newcomers go up to the mountain. The ratio tourists-mountain/ tourists-plain is back to normal. So the equilibrium is "displaced" towards the mountain.

Similarly, in chemistry:

An increase of the concentration of a reagent favours the reaction from left to right (which tends to eliminate this reagent). A decrease the concentration of a reagent favours the reaction from right to left (which tends to produce this reagent) An increase of the concentration of a product favours the reaction from right to left (which tends to eliminate this product). A decrease of the concentration of a product favours the reaction from left to right (which tends to produce this reagent)

### Influence of the pressure

In order to recover from the working stress in plain, some persons make holidays in the mountain. That's a quite normal equilibrium.

As the stress grows in plain, more and more go to the mountain. The equilibrium is "displaced" towards the mountain.

Similarly, in chemistry:

An increase of total pressure favours the reaction producing a decrease of pressure. An decrease of total pressure favours the reaction producing a increase of pressure.