Equilibrium Flashcards
When has equilibrium been reached?
When the forward and backward reactions occur at the same rate
How do you know if a reaction can be at equilibrium?
Equilibrium reactions will always have a double arrow (⇌)
What is Kc and what do Kc expressions tell us?
Kc = equilibrium constant
Kc expressions tell us whether there are more products or reactants being formed in an equilibrium reaction
What are the units for Kc?
There are none
What is the only state Kc can work for?
Gases
What does [___] mean?
Concentrations of ___
What is the Kc formula?
Kc = [products] / [reactants]
What happens if there is a number in front of a molecule in Kc expressions?
The number turns into a power
Eg, [2NO(g)] becomes [NO(g)]^2
What do you do if there is a solid or liquid in a Kc expression?
Ignore and eliminate it
What will the Kc value tell us?
The ratio of [products] to [reactants]
What can and can’t a Kc tell us?
How far a reaction has proceeded but not how fast
What are Kc values dependent on?
Temperature (must always remain constant)
What do the numerator and denominator values of Kc tell us?
A higher numerator value means there are more products being formed than reactants, so therefore a forward reaction is favoured
A higher denominator value means there are more reactants being formed than products, so therefore a backward reaction is favoured
When is a Kc value large or small and what reactions will that favour?
Kc equals:
- Large if it is >1 and will favour the forward reaction
- Small if it is <1 and will favour the backward reaction
What are the factors affecting equilibrium?
Concentration, temperature, pressure and catalysts
Describe concentration affecting equilbirum
Changing the concentration will drive the equilibrium to the side that will oppose the change
Describe temperature affecting equilbirum
Changing the temperature will drive the equilibrium to the side that will oppose the change
Describe pressure affecting equilibrium
Changing the pressure will drive the equilibrium to the side that will oppose the damage
Describe catalysts affecting equilibrium
Catalysts can speed up the time it takes for equilibrium to be reached, but does not directly affect equilibrium
What is dynamic equilibrium?
Dynamic equilibrium is when the number of reactants turning into products is the same as the number of products turning into reactants. Sometimes there will be more reactants left over and sometimes there will be more products left over.
What is Le Chatelier’s Principle?
Equilibrium moves in the direction that reduces change
What is self-ionisation of water?
Water constantly self-ionises in an equilibrium system where it produces both hydronium and hydroxide ions in equal amounts
