6: Equilibrium and Kc Flashcards
What is dynamic equilibrium?
When does it happen?
Concentration of products and reactants stays the same.
Only happens in a closed system.
Define Le Chateliers Principle.
If a reaction at equilibrium is subjected to change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change.
If equilibrium is in the forward direction, which reaction will be faster?
The forward reaction will be faster.
What happens to an equilibrium system if you increase the concentration of reactants?
Equilibrium shifts right to try and raise the concentration of products and counteract the change.
What happens if you decrease the concentration of reactants in an equilibrium system?
Equilibrium shifts left to try and raise the concentration of the reactants.
What happens if you increase the pressure in an equilibrium system?
Increase in pressure causes equilibrium to shift in the direction where there are fewer moles.
What happens if you decrease the pressure in an equilibrium system?
Equilibrium shifts in the direction where there are more moles.
What if you increase the temperature in an equilibrium system?
Equilibrium shifts in the endothermic direction to try and cool the reaction and counteract the change.
What if you decrease the temperature in an equilibrium system?
Equilibrium shifts in the exothermic direction to try and raise the temperature.
How do catalysts affect equilibrium?
No effect on equilibrium, they only speed up rate of reaction.
Write a Kc equation for the reaction H2 + I2 = 2HI
Kc = [HI]2 / [H2][I2]
What do square brackets represent in Kc?
Concentration
Before inputting numbers into Kc, what do you need to do?
Ensure all values are a measure of concentration.
How do you calculate units for Kc?
Cancel out the moldm-3 on the top of the equation and the bottom of the equation.
How will the Kc value change if you increase temperature and equilibrium shifts left in the endothermic direction towards reactants?
2SO2 + O2 = 2SO3
The reaction tries to absorb energy and cool the surroundings down. The amount of reactant produced therefore decreases, so its concentration falls.
Therefore, Kc will be lower.
