OVS SCH4U1 chapter 23 (23.5)

Le Chatelier’s principle

Define Le Chatelier’s principle

A principle of how systems respond to stress (changes in concentration, temperature, pressure) to equilibrium.

Stress to a chemical system at equilibrium that is then disturbed by a form of stress will respond to relieve the stress.

How does a system change its position of equilibrium when disturbed?

Shift to the right

• favouring products

  • Reactants dec

  • Products inc

• Favouring forward reaction

shift to the left

• favouring reactants

  • Reactants inc

  • Products dec

• Favouring reverse reaction

What is the effect of concentration if the products increase?

POE favours reverse reaction

What is the effect of concentration if the reactants increase?

POE favours forward reaction

What is the effect of concentration if the reactants descrease?

POE favours reverse reaction

What is the effect of concentration if the products decrease?

POE favours forward reaction

In an exothat is the effect of temperature if ?

In an exothermic reaction, what is the effect of temperature if heat is removed?

POE favours forward reaction (exothermic)

In an endothermic reaction, what is the effect of temperature if heat is added?

POE favours reverse reaction (exothermic)

In an endothermic reaction, what is the effect of temperature if heat is removed?

POE favours forward reaction (endothermic)

What states of matter have no impact on the equilibrium of a solution (2)

1. Solids

2. Pure liquid

What must be determined before the effect of pressure can be solved?

The collective mols of the reactants and the collective mols of your products

• add up coefficients = mols

What must be determined before the effect of pressure can be solved?

The collective mols of the reactants and the collective mols of your products

• add up coefficients = mols

Which reaction does the Position of Equilibrium (POE) favour when the pressure decreases?

Pressure decreases = POE favours reaction with fewer mols