C5.3 - Equilibria

Question 1

What is equilibrium and dynamic equilibrium?

Answer 1

A situation in a reversible reaction in a closed system in which the rates of the forward reaction and backward reaction are equal, and the concentrations of the products and reactants remain constant

Dynamic - In terms of equilibrium - The forwards and backwards reactions are still occurring.

Question 2

What does an equilibrium position on the left and right tell you?

Answer 2

• The equilibrium position is on the left when the
  concentration of reactants is greater than the
  concentration of products.
• The equilibrium position is on the right when the
  concentration of the reactants is less than the
  concentration of the products.

Question 3

What happens to the equilibrium position as you increase pressure?

Answer 3

If the pressure is increased, the equilibrium position moves in the direction of the fewest gaseous moles as shown in the balanced equation for the reaction.

Question 4

What happens to the position of equilibrium as the concentration of a substance is increased?

Answer 4

If the concentration of a substance is increased, the equilibrium position moves in the direction away from the substance as shown in the balanced equation for the reaction.

Question 5

What happens to the equilibrium position if you increase the temperature?

Answer 5

• If the temperature is increased, the position of
  equilibrium moves in the direction of the
  endothermic change.

Question 6

What is the equilibrium yield?

Answer 6

The equilibrium yield is the amount of the desired product present in a reaction at equilibrium.

Question 7

What is Le Chatelier’s principle?

Answer 7

When a change is made to a reaction at equilibrium, the position of equilibrium moves to oppose the change.

Question 8

Why do you need a compromise pressure for the equilibrium yield of methanol?

Answer 8

• High pressures need expensive equipment to
  compress the gases, lot of energy to run and
  tough reaction vessels to withstand the
  pressure.
• Compromise pressure - High enough to achieve a
  reasonable equilibrium yield, not so high to be
  expensive or hazardous.

Question 9

Why do you need a compromise temperature for the equilibrium yield of methanol?

Answer 9

Low temperature - Rate of reaction is too low to produce methanol quickly enough to be profitable.

Compromise temperature - Temperature low enough to achieve a reasonable equilibrium yield of methanol, but high enough to achieve a reasonable rate of reaction.