3.1.6.1 Chemical Equilibria and Le Chatelier's Principle Flashcards
What is equilibrium?
When the forwards reaction and backwards reactions are at the same rate
Relates to reversible reactions
Temperature favours the endothermic reaction
Concentration favours the reaction that produces fewer molecules
For a reaction to reach equilibrium, it must be in a closed system (nothing enters or leaves)
In business they take the product away which stops the reaction from reaching equilbrium
What is Le Chatlier’s principle?
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the distrubance
What is the effect on the equilibrium yield if a catalyst is present?
No effect
It increases the rate of the backwards and forwards reaction by the same ratio
What is the difference between a homogeneous and heterogeneous system?
In a homogeneous system the components are at the same state but in a heterogeneous system they are in two or more states
How do you determine the enthalpy change of the backwards reaction in an equilibrium when given the forward reactions enthalpy change?
If the forward reaction is exothermic, the reverse reaction is endothermic by the same amount
What happens when you add reactants to an equilibrium?
The position of equilibrium has moved to the right and the yield has increased
System decreases the concentrations of reactants and increased the concentrations of products
What happens when you add products to an equilibrium?
More product is broken down so the equilibrium position is moved to the left
Yield decreases
What happens when you increase temperature in an equilibrium?
It favours the endothermic reaction which will change the concentrations of reactants and products
In an exothermic forward reaction: position moves to the left, yield decreases, reactant concentration increases, product concentration decreases
The concentrations changing reduces the temperature
What happens when you increase pressure in an equilibrium?
The position of equilibrium moves towards the side with fewer moles of gas
If there are the same number of moles on either side, there is no change
Does a catalyst change the position of equilibrium?
A catalyst speeds up both the forward and backward reactions to the same extent so has no overall effect
It does speed up the rate at which equilibrium is reached
