4.2 Equilibrium Flashcards
What happens to the concentrations of reactants and products at dynamic equilibrium?
They remain constant. This is because the forward ad backward reactions are happening at the same rate
What is Le Chatelier’s principle?
if a small change is applied to a system at equilibrium, the position of the equilibrium moves in such a way to minimise the effect of the change
What is the effect of increasing pressure on a system at equilibrium?
The equilibrium moves in the direction with fewer moles of gas
What is the effect of increasing the concentration of a substance on a system at equilibrium?
The equilibrium will move in the opposite direction
What is the effect of increasing the temperature on a system at equilibrium?
The equilibrium will move in the direction of the endothermic process
What is the effect of introducing a catalyst to a system at equilibrium?
They reduce the time taken to reach equilibrium but do not affect the position of it
What is the equilibrium constant?
It is a value that describes the position of equilibrium for a reaction at a given temperature
What is used to calculate the value of Kc?
The equilibrium concentrations of the reactants and products
How is the Kc expression written?
reactants
How do you work out the units for Kc?
Add together the powers on the top to get X
Add together to powers on the bottom to get Y
Y - X = Z
Raise moldm-3 to Z to get the units
What do you often have to work out before being able to work out Kc?
The equilibrium concentrations, using the starting concentrations and the balanced equation
What is the value of Kc in the reverse reaction?
It is the reciprocal of the forward value. The units will also change
What is the effect of catalysts on Kc?
They do not change the value. This is because they increase the rate of the forward and backward reaction by the same ratio.
What is the effect of concentration on Kc?
The equilibrium will shift to oppose the change so Kc will not be affected
How will increasing temperature affect Kc in an exothermic process?
Kc will decrease
