C5.3

Question 1

What is a reversible reaction?

Answer 1

When the products can break down and reform the reactants at the same time as being formed
Two reactions occur simultaneously

Question 2

What is dynamic equilibrium?

Answer 2

When a reversible reaction happen in a closed system, the rates of the forwards and backwards reaction becomes equal
As the reactions still occur it is dynamic
No observable changes in quantities
NOT when the quantities are equal

Question 3

What is the equilibrium position? What does it mean when it’s on the left or right?

Answer 3

Gives you an idea of the ratio of the equilibrium concentrations of the products to reactants
LEFT = concentration of reactants is greater than concentration of products
RIGHT = concentration of products is greater than concentration of reactants

Question 4

What happens if you change the pressure?

Answer 4

Increased pressure means the position moves to the side with fewest moles of GAS in a balanced equation
If you decrease the pressure equilibrium moves to the side with more gas particles
1) count number total number of moles of gas on each side of the equation
2) whichever has less is the side the equlibira position moves to

Question 5

What happens if you change the concentration?

Answer 5

If concentration is increased equilibrium moves in the opposite direction
If concentration is decreased equilibrium stays on the same side to replace the missing reactant

Question 6

What happens if you change the temperature?

Answer 6

If temperature is increased, equilibria moves in the direction of the endothermic change
If you decrease the temperature equilibrium goes to the exothermic side
If Delta H = negative then the forwards reaction is exothermic

Question 7

What is the equilibrium yield?

Answer 7

The quantity of the desired product present in a reaction at equilibrium

Question 8

What are the desired conditions for the production of methanol and how would you compromise?
CO(g) + 2H2(g) >< CH3OH(g)
Delta H = -91

Answer 8

• high pressure (increased products)
• low temperature
  BUT
  high pressure costs a lot to ensure it isn’t dangerous, use of expensive equipment
  low temperatures decrease the rate of reaction

Question 9

What are the 3 factors you have to compromise with?

Answer 9

• yield
• cost
• rate

Question 10

What is Le Chantelier’s principle?

Answer 10

“ for a closed system at equilibrium, if a change is made, the position of the direction will oppose the change