Equilibrium Changes (Le chatelier's principle)

Question 1

Adding a catalyst to an equilibrium System

Answer 1

1. speeds up the rate of both the forward and reverse reaction equally.
2. The ratios of products to reactants remains the same. (Kc is unchanged)
3. Equilibrium is reached faster.

Question 2

removing the product

Answer 2

1. If the sulfur trioxide is removed as it is produced, [SO3] will decrease, so the equilibrium will move to minimise the change (stress placed on the system).
2. This means the reaction will move forward to replace the lost sulfur trioxide.
   3This will increase the yield of the desired product.

Question 3

increasing product

Answer 3

1. Adding water to this equilibrium means there has been an increase in (concentration of) a product.
2. The system will react to reduce this change, so the reverse reaction will be favoured to use up some
   of the extra product.
   3 This results in an increased concentration of the pink
   [Co(H2O)6 2+ ion, so the solution will turn pink or the pink colour will intensify.

Question 4

increasing the reactant

Answer 4

1. Adding more of the reactant would increase the concentration of the reactant, so the reaction moves in the forward direction/favours the products to use up the added acid,
2. so the colour of the solution will become more orange.

Question 5

decreasing the reactant

Answer 5

1. decreasing the reactant would decrease the concentration of the reactant, so the equilibrium will move to minimise the change
2. this means the reaction will move in the reverse direction to replace the lost reactant
3. this will increase the yield of the desired product/or colour of the solution will turn colour of reactants

Question 6

Increasing the pressure

Answer 6

1. equilibrium will shift in the direction that has fewer gas molecules (moles) in order to decrease the pressure
2. because reactant side has this many moles and the product side has this many moles
3. this will cause the colour to go the colour of the side with less moles

Question 7

decrease pressure

Answer 7

1. equilibrium will shift in the direction that has more gas molecules (moles) in order to increase the pressure
2. because the reactant side has this many moles and the product side has this many moles
3. this will cause the colour to go the colour of the side with fewer moles

Question 8

increase temperature

Answer 8

1. the equilibrium will shift in the direction of the endothermic reaction (to absorb the added heat) in order to decrease the temperature.
2. Because this reaction is endothermic/exothermic (positive or negative ∆H value), the
   exo/endo direction will be backwards, so the colour of the solution will become pink or the pink colour will intensify.

Question 9

decrease temperature

Answer 9

1.decreasing the temperature will cause the reaction to move in the exothermic direction to
compensate for the loss of heat energy into
surroundings.
2. Because this reaction is endothermic/exothermic
(positive or negative ∆H value), the
exo/endo direction will be backwards, so the colour of the solution will become
pink or the pink colour will intensify.