Le Chatelier’s Principle & Collision theory

Le Chatelier’s Principle allows us to predict how a chemical system at equilibrium will change in response to external factors. Understanding this concept in terms of Collision theory will allow you to make predictions with sound scientific reasoning.

• Explain the overall observations about equilibrium in terms of the
collision theory

Learn.

When an external stress (change in temperature, pressure, concentration) is applied to a system in equilibrium. The system will respond in a way which minimizing the effect of the change. This is La Chatelier’s principle.

Collision theory explain chemical reactions as successful collisions between reactant molecules, increasing the temperature or number of reactants increases the likely-hod of a successful collision occurring hence increasing the rate of reaction.

Collision theory can be applied to La Chatelier’s principle’s as follows:

Le Chatelier’s Principle & Collision theory Questions

Question 1.

The following system is exothermic

Predict what will happen to the K eq if the temperature of the system is decreased – explain why this occurs with respect to collision theory. [4 marks]

Question 2.

The following system is exothermic

“The above reaction will cease to occur when the system is at equilibrium and increasing the temperature will make the reverse reaction start up again.”

Evaluate the validity of the students statement making reference to collision theory [8 marks]

Question 3.

Which of the following explains in terms of collision theory what would happen to a system if reactants were increased.

a) Increasing reactants pushes the equilibrium towards the products since more successful collisions can occur between reactants hence increasing the rate of the forward reaction.

b) Increasing reactants pushes the equilibrium towards the reactants as fewer successful collisions can occur between reactants hence decreasing the rate of the forward reaction.

c) This decreases products pushing the equilibrium towards the reactants since more successful collisions can occur between products hence increasing the rate of the reverse reaction.

d) Increase the rate of both the reverse and forward reaction equally hence no net change in reaction rate. This occurs since less energy is required for a successful collision