Equilibria Flashcards
What happens to the forwards reaction and the backwards reaction when the reactants get used up
Forwards slows down
Backwards speeds up
Dynamic equilibrium
Concentrations of reactants and products stay constant
Rate of forwards reaction= rate of backwards reaction
So amounts of reactants and products don’t change
Closed system
Equilibrium constant, Kc
How far to the left or right the equilibrium is
Homogenous system
A system in which everything is in the same physical state
aA + bB === dD + eE (homogenous equilibria)
Kc= [D]d[E]e divided by [A]a[B]b
Lower case= number of moles of each substance
Brackets mean concentration
Heterogenous equilibria and Kc
Not everything is in the same physical state
Do not include solids or pure liquids in the expression for Kc because their concentrations stay constant
Why aren’t catalysts included in the equilibrium
Catalysts don’t affect equilibrium concentrations of the products or the reactants (they just speed up the rate at which dynamic equilibria is reached)
Le Chat principle
If there’s a change in concentration, pressure and temperature, the equilibrium will move to counteract the change.
Increase concentration of reactant
Equilibria shifts to right
To make more product (to get rid of reactant)
Increase concentration of product
Equilibria moves to left
To get rid of extra product and produce more reactants
Reverse reaction faster
Decreasing concentrations
Opposite effect
Increasing pressure
Equilibria shifts in direction with fewer gas molecules
To reduce the pressure
Decreasing pressure
Equilibrium shifts to side with more gas molecules
Increases pressure
Increasing temperature
Equilibrium shifts in the endothermic direction to absorb the heat
Decreasing temperature
Equilibrium shifts in exothermic direction to try replace the heat
Explain why a catalyst is used in this industrial process
Lower the activation energy
Increase rate at which the reaction moves towards equilibria
Less energy costs/ milder conditions
Explain any change in the position of equilibrium if a few drops of sodium hydroxide solution are added
2CrO4^2- + 2H+ ——> Cr2O2^2- + H2O
OH ions combined with/ neutralise the H+ ions to remove them from the equilibrium
Shifts to left to use up reactants
(Haber process)
Give 3 reasons why the product may be removed before it’s maximum concentration is achieved
Equilibrium shifts to right
Removal decreases rate of backwards reaction
Time to attain equilibrium may be too long
Uncreated reactants can be recycled
