Le Chatelier's Principle

According to Le Chatelier’s Principle, when a system (chemical reaction) has its equilibrium position altered by changes in concentration, temperature, pressure or volume it will shift in the forward or reverse direction to minimize the these changes. 

Le Chatelier’s Principle

Le Chatelier’s Principle Basics

Under Equilibrium Law, when a chemical reaction shifts in the forward direction to offset changes made to its equilibrium position the product side will increase and the reactant side will decrease. 

Dynamic-Equilibrium-Forward-Direction-Counteract-Disturbed-Adjust-ModeratedEquilibrium Shift (Forward Direction)

When a chemical reaction shifts in the reverse direction to offset changes made to its equilibrium position the product side will decrease and the reactant side will increase. 

Equilibrium-shift-reverse-changing-the-conditionsEquilibrium Shift (Reverse Direction)

Reactants and Products 

When we add reactants or remove products the chemical reaction will shift in the forward direction to re-establish equilibrium. This causes an increase in the products and a decrease in the reactants. 

Products-Reactant-Forward-DirectionProducts and Reactants (Forward Direction)

When we remove reactants or add products the chemical reaction will shift in the reverse direction to re-establish equilibrium. This causes a decrease in the products and an increase in the reactants. 

Products-Reactants-ReverseProducts and Reactants (Reverse Direction)

Pressure and Volume 

Pressure and volume are inversely proportional to one another. Increasing the volume means decreasing pressure. In this situation the reaction will shift to the side with more moles of gas

Volume-vapor-pressure-forwardVolume and Pressure (Forward Direction)

Decreasing the volume results in an increasing pressure. In this situation the reaction will shift to the side with less moles of gas

Volume-Pressure-ReverseVolume and Pressure (Reverse Direction)

Temperature 

In an exothermic process, heat is released and in a chemical reaction is written as a product. 

Le-Chatelier-Principle-ExothermicLe Chatelier's Principle (Exothermic Reaction)

In an endothermic process, heat is absorbed and in a chemical reaction is written as a reactant. 

Le-Chatelier-Principle-EndothermicLe Chatelier's Principle (Endothermic Reaction)

When the temperature is increased the chemical reaction will shift away from heat

Increasing-TemperatureLe Chatelier's Principle (Increasing Temperature)

When the temperature is decreased the chemical reaction will shift towards the heat

Decreasing-TemperatureLe Chatelier's Principle (Decreasing Temperature)


Inert Gas

An inert gas represents a non-reactive gas usually in the form of a noble gas. When an inert gas is added under constant temperature there will be no shift in the equilibrium position.  

Inert-Gas-Le-Chatelier-Principle-Constant-TemperatureInert Gas (Constant Temperature)

When an inert gas is added under constant pressure then the reaction will shift to the side with more moles of gas

Inert-Gas-Le-Chatelier-Principle-Constant-PressureInert Gas (Constant Pressure)


Liquids, solids and catalysts

The addition of liquids, solids, or a catalyst causes no change or shift in the equilibrium position. 

Le-Chatelier-Principle-solid-liquid-catalystLe Chatelier's Principle (Liquids, Solids, Catalysts)

Further Applications

Le Chatelier’s Principle plays an essential part in our understanding of chemical equilibrium when discussing the different forms of the equilibrium constant (Ksp, Keq, Kc), dealing with ICE Charts, and comparing Q and K.