Le Chatelier's Principle

When a chemical system at equilibrium is exposed to stress, it responds by:

• Doing nothing - everything will work out.

• Shifting to oppose the change.

• Releasing chemicals into its environment to stop the stressor.

• The reaction will stop until stress is stopped.

Stresses on a chemical system include all of the above, except:

• Change in concentration

• Change in pressure or volume

• Change in states of matter

• Change in temperature

Which of the following changes in concentration will favour the forward reaction, and shift RIGHT:

• Increasing the concentration of products OR decreasing the concentration of reactants

• Increasing the concentration of reactants OR decreasing concentration of the products

• Increasing the concentration of the reactants AND products

• Decreasing the concentration of reactants AND products

Which of the following changes in concentration will favour the reverse reaction, and shift LEFT:

• Increasing the concentration of products OR decreasing the concentration of reactants

• Increasing the concentration of reactants OR decreasing concentration of the products

• Increasing the concentration of the reactants AND products

• Decreasing the concentration of reactants AND products

Which of the following changes in volume and pressure will result in a shift towards the side of the reaction with MORE gas molecules:

• Decreasing volume OR decreasing pressure

• Increasing volume OR increasing pressure

• Increasing pressure OR decreasing volume

• Increasing volume OR decreasing pressure

Which of the following changes in volume and pressure will result in a shift towards the side of the reaction with LESS gas molecules:

• Decreasing volume of container OR decreasing pressure

• Increasing volume of container OR increasing pressure

• Increasing pressure OR decreasing volume of container

• Increasing volume of container OR decreasing pressure

In an EXOTHERMIC reaction:

• Increasing the temperature will cause a shift to the RIGHT

• Increasing temperature will cause a shift to the LEFT

• Increasing temperature will cause NO shift

• Decreasing temperature will cause a shift to the LEFT

In an ENDOTHERMIC reaction:

• Increasing temperature will cause a shift to the RIGHT

• Decreasing temperature will cause NO shift

• Decreasing temperature will cause a shift to the RIGHT

• Decreasing temperature will cause a shift to the LEFT

​ Which variables below will cause no equilibrium shift, if added to a chemical system?

• Products and reactants

• Inert gases and catalysts

• Heat sources and pressure changes

What would the equilibrium shift be in the following chemical equation, if HEAT ENERGY was ADDED:

heat + N2O4(g) <-> 2NO2(g)

• Left

• Right

• No change