Le Chatelier's Principle

Question 1

What is Le Chatelier’s principle

Answer 1

When a change is made to an equilibrium system, the system will proceed in a way that will partially oppose the effect of the change
Factors that can disturb equilibrium:
- addition/removal of products/reactants
- changes in temperature
- changes in volume/pressure

Question 2

Effect of adding products/reactants

Answer 2

If the volume of system has not changed, + a reactant/product increases the concentration of the reactant/product
- the system partially opposes this change by favouring the reaction that will decrease the concentration of the reactant/product
- will then re-establish equilibrium
- the concentration of the added species will be more than initial equilibrum

Question 3

Application of Collision Theory

Answer 3

Increase in reactants –> more reactant particles with more collisions –> increased RoR
- same for products –> increase RoR of the re-formation of reactants

Question 4

Effect of removing products/reactants

Answer 4

Will cause the system to favour the reaction that will increase the concentration of the reactant/product
- removing products –> favours forward reaction
- removing reactants –> favours backward reaction

Question 5

Effect of a catalyst

Answer 5

• speed up a reaction without being consumed
• does not affect PoE

Question 6

Effect of concentration on equilibrium

Answer 6

• +/- substances which increases/decreases conc. of substance being added
• increasing/decreasing volume which increases/decreases the conc. of all species in the system
• dilution which for solutions, decreases concentration of all species

Question 7

Increasing/decreasing volume

Answer 7

Decrease volume
- instantaneous increase in the concentration of all species
- will favour the reaction that produces the least nnumber of particles –> to decrease conc.

Increase volume
- instantaneous decrease in the concentration of all species
- favour the reaction that produces more particles due –> to increase conc.

Question 8

Effect of pressure on equilibrium

Answer 8

Occurs with a change of volume in the system
- decrease in volume = increase in pressure –> will favour the reaction that produces the least no. of particles
- increase in volume = decrease in pressure –> will favour the reaction that produces the most no. of particles

Question 9

Effect of temperature on equilibrium - Endothermic

Answer 9

Increase in temp. –> increases kinetic energy –>more particles that can satisfy AE –> increase in no. of collisions –> increases RoR of both reactions
- favours the forward reaction

Decrease in temp.
- favours the backward reaction

Question 10

Effect of temperature on equilibrium - Exothermic

Answer 10

Increase in temp. –> increases kinetic energy –>more particles that can satisfy AE –> increase in no. of collisions –> increase RoR of both reactions
- favours the backward reaction

Decrease in temp.
- favours the forward reaction