CHP 6: Le Chatelier's Principle

Le Châtelier’s principle

states that if a change in conditions is applied to a system at equilibrium, the system changes or shifts in the direction that relieves the stress.

Changes in pressure and volume

affect the number of moles in the gaseous reactants and gaseous products.

Pressure

An increase in - (due to a decrease in volume) results in a reaction in the direction of fewer mol

Pressure

A decrease in - (due to an increase in volume) results in a reaction in the direction of a greater number of moles.

Heterogeneous equilibrium

For a - -, pressure changes have no effect.

Inert gas

Addition of a - - does not affect the composition of the equilibrium mixture.

Decreasing

- the volume shifts the reaction in the direction with fewer moles of gas molecules.

Increasing

- the volume shifts the reaction in the direction with the greater moles of gas molecules.

Temperature

Increasing the - causes the equilibrium position of a reaction to shift in the direction that absorbs heat. A - change always changes the equilibrium constant.

Catalysts

Increase the rate of a chemical reaction; however, they do not affect the amount of reactants and products in the equilibrium.

Activation Energy

Adding a catalyst lowers the - by the same amount for both reactions.

Equilibrium system

In an - , a reversible chemical reaction occurs when the rate of the forward reaction is equal to the rate of the reverse reaction