Le Chatelier's Principle

Chapter 3: Chemical

Equilibrium

Section 2: Factors Affecting

Chemical Equilibrium

Applying Le Châtelier’s Principle

Changes in

Concentration

Pressure

Temperature

Applying Le Châtelier’s Principle

• Adjusting the concentrations of either the reactants or the products put a stress on the equilibrium.

• Adding reactants increases the number of effective collisions between molecules and upsets (disturb)

the equilibrium.

Adding Reactants

Removing Products

Adding Products

Changes in Concentration

Changes in Concentration

Adding products

The equilibrium shifts to the left and results in additional reactant.

What if we

keep removing

[decreasing]

CO?

Changes in Concentration

Adding Reactants/ Removing products

That is, the equilibrium shifts to the right and results in additional product.

What if we

keep removing

[decreasing]

H2O?

3. When a reactant removed
the reaction shifts to the left

4. When a product is added
the reaction shifts to the left

Equilibrium shifts to the left

Equilibrium shifts to the left

Changes in Concentration

Removing Reactants / Adding Products

Applying Le Châtelier’s Principle

Changes in

Concentration

Pressure

Temperature

Changes in Pressure

500 mL

100 mL

Which one will be more sweety?

When volume decreased, we
get higher concentrations

Changes in Pressure

Moles of reactant versus moles of product

4 moles

2 moles

Apply Le Châtelier’s principle

The equilibrium can relieve the stress of increased pressure by shifting to the right.

Which side has more pressure?

Reactant

Changes in Volume & Pressure

Moles of reactant versus moles of product

4 moles

2 moles

If the number of moles of gas is the same on both sides of the equation, changes in volume
and pressure have no effect on the equilibrium.

Applying Le Châtelier’s Principle

Changes in

Concentration

Pressure

Temperature

Temperature and Keq

Temperature

Any change in temperature results in a change in Keq

the larger the value of K eq , the more product is found in the equilibrium mixture

Heat and equilibrium position

Temperature

Reaction is Exothermic

If heat of the system decreased, the rection will go to the right
If heat of the system increased, the rection will go to the left

Catalysts