Dynamic Equilibrium Flashcards
(15 cards)
what is a reversible reaction
a chemical reaction that has a forward and reverse reaction
what is dynamic equilibrium
exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction
what are characteristics of dynamic equilibrium
rate of forward + reverse reactions are the same
the conc of reactants + products do not change (can measure using a ph probe)
only applies if a system remains isolated
what does equilibrium position tell us
lies to right - more product than reactant in the mixture
lies to left - more reactant than product in the mixture
it is desireable for equilibrium position to be as far right as possible to achieve a high yield of product
the conc of reactants and products does not change at equilibrium
what is le Chateliers principle
when a system in dynamic equilibrium is subjected to a change, the equilibrium position will shift to minimise the change
how do you know if a forward reaction is favoured
equilibrium position shifts to right - more product + less reactant at new equilibrium
how do you know if a reverse reaction is favoured
equilibrium position shifts to left - more reactant + less product at new equilibrium
what is a model answer for factors effecting dynamic equilibrium
- state which reaction is favoured (forward or reverse) - concentration
- state which side has more / less moles of gas + which way is favoured - pressure
- state whether forward reaction is exothermic / endothermic + which is favoured - temperature
- state which way equilibrium position shifts (left or right)
- state what is minimised as a result (get this from question)
- state what happens to equilibrium composition (more / less, reactant / product)
what is the effect of concentration on dynamic equilibrium
the forward reaction is favoured
equilibrium position shifts to right
to minimise the increase in X concentration
less reactant + more product at new equilibrium
(opposite for reverse)
what is the effect of pressure on dynamic equilibrium
less moles of gas on the right
forward reaction is favoured
equilibrium position shifts to right
to minimise the increase in pressure
less reactant + more product at new equilibrium
(opposite for reverse)
what is the effect of temperature on dynamic equilibrium
the forward reaction is exothermic
the endothermic reaction is favoured, which is the reverse reaction
equilibrium position shifts to the left
to minimise the increase in temperature
more reactant + less product at new equilibrium
(opposite for reverse)
what is the effect of a catalyst on dynamic equilibrium
it does not affect it
a catalyst speeds up rate of forward + reverse reactions equally + increases the rate at which equilibrium is established
what is the equilibrium law for a reaction
mA (aq) + nB (aq) <ā> pC (aq) +qD (aq)
what is the equilibrium constant
Kc = [products] / [reactants]
[] = concentration
a large value = more products, equilibrium lies to right
a small value = more reactants, equilibrium lies to left
units may vary
what is the equilibrium expression
Kc = [C]^p x [D]^q / [A]^m x [B]^n
