Chemical Equilibria

Question 1

What is Dynamic Equilibria?

Answer 1

The rate of the forward reaction is the same as the rate of the reverse reaction in a closed system.

Question 2

What factors affect the position of equilibrium?

Answer 2

• Concentration
• Pressure
• Temperature
• Catalysts

Question 3

What is Le Chatelier’s Principle?

Answer 3

Le Chatelier’s principle states that when a system in dynamic equilibrium is subjected to change, the position of equilibrium will shift to minimise the change.

Question 4

How does concentration affect equilibrium?

Answer 4

• If the concentration of the reactants is increased,
• the position of equilibrium will shift to the right,
• this will cause the concentration of products to increase to oppose this change,
• causing an increase in the product yield.

(Inverse for decreasing conc.)

Question 5

How does pressure affect equilibrium?

Answer 5

• An increase in pressure is caused by a decrease in volume,
• this will cause the position of equilibrium to shift towards the side with fewer gaseous moles,
• as this will oppose the change by causing a decrease in pressure,
• this would cause an increase in product yield.

(Inverse for decreasing pressure)

Question 6

How does temperature affect equilibrium if the forward reaction is exothermic?

Answer 6

• If the temperature of a reaction is increased and the forward reaction is exothermic,
• The position of equilibrium will shift to the left, in the direction of the endothermic reaction,
• as this will cause a decrease in temperature,
• therefore, more reactants are made.

(Inverse for decreasing)

Question 7

How does temperature affect equilibrium if the forward reaction is endothermic?

Answer 7

• If the temperature of the reaction is increased when the forward reaction is endothermic,
• The position of equilibrium will move to the right, in the direction of the endothermic reaction,
• as this will cause a decrease in temperature,
• therefore, more products are made.

(Inverse for decreasing)

Question 8

What is the affect of a catalyst on equilibrium?

Answer 8

• A catalyst does not change the position of equilibrium as the catalyst just increases the rate at which equilibrium is established.

Question 9

What are the best conditions for the Haber process and why?

Answer 9

• 350-500°c
• 100-200atm
• iron catalyst
  —> this speeds up the reaction so that lower temperatures can be used and operating costs are reduced.