3.2.3 Flashcards
What is a state of dynamic equilibrium?
When, in a closed system, there is no macroscopic differences in the system, as the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of the reactants and products remain constant.
How the the position of the equilibrium effect it’s yield?
If the position lies to the right, the yield of the products will be high.
If the position lies to the left, the yield of the products will be low.
What is le Chatrlier’s Principle?
(Definition not required)
This states that if a change occurs in a reversible reaction, the equilibrium shifts in the direction which opposes the change.
The effects of changing the concentration on the equilibrium
Adding the reactants and removing the product favours the forward reaction.
Removing the reactants and adding the product favours the backwards reaction.
The effect of changing the pressure on the equilibrium
(Only effects reactions between gases)
Increasing the pressure favours the reaction with fewer moles.
Decreasing the pressure favours the reaction with more moles.
The effect of changing the temperature on the equilibrium
Increasing the temperature favours the endothermic reaction.
Decreasing the temperature favours the exothermic reaction.
The effect a catalyst on the equilibrium
A catalyst speeds up the rate of the forward and backwards reactions in an equilibrium equally so does not change its position. However, the rate at which the equilibrium is reached will increase.
(d) the techniques and procedures used to investigate changes to the position of equilibrium for changes in concentration, temperature, and in the presence of a catalyst.
Nitrogen dioxide (reddish brown) <-catalyst?-> N2O2 (colourless)
2H+ + 2CrO4 2- (yellow) <-> Cr2O7 2- (orange) + H2O
Blue -> white
Anhydrous copper sulphate <-> hydrated copper sulphate
CuSO4 + 5H2O <-> CuSO4•5H2O
What happens to conditions set in industry?
A compromise between having a fast rate, so producing the product as fast as possible, and equilibrium yield, obtaining as high a yield as possible, in order to improve output of a product (profit) and reducing manufacturing costs.
Calculations for the equilibrium constant
Kc = [products]^moles / [reactants]^moles
How does Kc relate to the position of equilibrium?
When Kc > 1 there are more products than reactants, so the equilibrium lies to the right.
When Kc < 1 there are more reactants then products, so the equilibrium lies to the left.
When Kc = 1 equilibrium lies halfway between the reactants and products.
