3.1.2 Factors that affect equilibrium

Question 1

when is a system at equilibirum?

Answer 1

when the rate of the forward reaction is equal to the rate of the reverse reaction

Question 2

what are the 3 stresser’s that cause a system at equilbrium to shift according to Le Chatelier’s principle?

Answer 2

1. concentration increase/decrease
2. pressure with gases only (achieved by change in volume)
3. temperature increase/decrease

Question 3

what is the effect of changing concentration to a system at equilibrium? Explain using collision theory

Answer 3

1. identify the stress
   - the equilibrium is distured by an increase/decrease in concentration
2. link to collision theory
   - increase causes increased successful collisions between reactants/products (depending on where stress is)
   - decrease causes decreased successful collisions between reactants/products (depending on where stress is)
3. determine the shift
   - causing a shift to the reactants/products
   
   • shift away from increase
   • shift towards decrease
4. identify the final result
   - moving to reactants will increase reactants and decrease products
   - moving to products will decrease reactants and increase products

Question 4

what is the effect of changing volume to a system at equilibrium? Explain using collision theory

Answer 4

1. identify the stress
   - the equilibrium has been distured by an decrease/increase in volume
2. link to collision theory
   - increase causes increased successful collisions for both the forward and reverse reactions
   - decrease causes decreased successful collisions for both the forward and reverse reactions
3. determine the shift
   increase in pressure:
   - causing a shift the the side with less moles (products/reactants)
   decrease in pressure:
   - causing a shift to the side with more moles (reactants/products)
4. identify final result
   - increase/decrease in reactants and increase/decrease in products

Question 5

what is the effect of changing temperature to a system at equilibrium? Explain using enthaly.

Answer 5

1. Identify the stress
   - There has been an increase/decrease in temperature
2. Connect to enthalpy
   - the enthalpy indicates the forward direction is exothermic (delta H is negative)/endothermic (delta H is positive)
3. determine the shift in the reaction
   - results in the reverse direction as an increase will shift in the exothermic direction, causing a shift to the left/products
   - results in the forward direction a decrease will always shift in the exothermic direction causing a shift to the right/products
4. Identify the results
   - causing a decrease in products and increase in reactants
   OR
   - causing an increase in produts and decrease in reactants

Question 6

How is the equilibrium position altered when a catalyst is added?

Answer 6

1. lowers the activation energy of both the forward and reverse reactions
2. no effect on the equilibrium
3. allows the system to achieve equilibrium faster