Equilibrium Flashcards
(25 cards)
macroscopic equilibrium
When two reactants are added in a container - after time they stop changing colour
Microscopic Equilibrium
The reaction continues in both directions at equal rates - no longer changes
When the forward rate = the reverse rate
what does K stand for
equilibrium constant
the ratio of products/reactants AT EQU
Small K = products/BIG reactants = little products formed
Large K = BIGproducts/reactants = little reactants left = a lot of product
what does it mean when K is very large
the reaction goes to completion
products > reactants in equilibrium
what does it mean when K = 5
significant amounts of reactants and products are present at equilibrium
Law of Chemical Equilibrium
When a system reaches equilibrium at a given temperature, the ratio of quantities that make up the reaction quotient has a constant numerical value
what is the Q
reaction quotient
- ratio of products/reactants at any time in the rxn
Tells us where the reaction is at this moment - K is the goal that the ratio is supposed to be at equilibrium
- At equilibrium Q = K
T/F Q and K are unitless
true
if a reaction has more than one elementary step you ____ the Q to get the overall Q
multiply each reaction Q values
this allows some of the terms to cancel out = intermediates
if a reaction has more than one elementary step you ____ the K to get the overall K
multiply
what does having a Qp and Kp mean
the question = partial pressures instead of concentrations
when does Kc = Kp?
Kp = Kc if the moles of the reaction stay constant (4 moles → 4 moles)
if the number of moles are not the same
Kp = Kc (RT)^moles of gas
moles of gas = nf - ni
what does a large/small Q mean
LARGE
products/reactants
smaller denominator = more products, less reactants
SMALL
bigger denominator = less products more reactants
Q < K
Q is smaller than K
A small Q is possible if the reactants are being favoured(the denominator is bigger than products)
If the reactants are larger, to counteract and try to balance the system will progress and favour the products (RIGHT) until Q = K
Reactants → Products
***Q will do whatever it can to become = to K
Q > K
Q is larger than K
large Q = BIGproducts/SMALLreactants
If the products are larger, to counteract, the system will progress to the LEFT - favouring the reactants
Reactants ← Products
**Q will do whatever it can to become = to K
Q = K
no net change
equilibrium
How to Use the Assumption
when the K is solved or given in the question
- if the initial reactant concentration is divided by the value of x that comes from the ICE table
- you can make this assumption if K is very small
- also if the division = less than 5%
Le Chatelier’s Principle
If a system at equilibrium is disturbed it will change and shift the equilibrium position in a direction that helps relieve the stress
Equilibrium is when Q = K, stress makes them not equal
what happens when you change the concentration of a substance in a reaction
when u increase the concentration - the system wants to consume it
↑ reactant - shift to products
↑ products - shift to reactants
↓ reactants - shift to reactants
↓ products - shift to products
what happens when you disturb the pressure/volume
↑ P ↓ V = to fewer moles
↓ P ↑ V = to more moles
Add inert gas - no change
doesn’t affect on LIQUIDS OR SOLIDS - cannot be compressed like gases
What does a change in temperature do to a reaction
Exo
↑ Temp = shift reactants - L
↓ Temp = shift products - R
Endo
↑ Temp = shift products - R
↓ Temp = shift reactants - L
what does the effect of temperature have on K
Exo
↑ Temp = small K
↓ Temp = large K
Endo
↑ Temp = large K
↓ Temp = small K
what is the only factor that impacts K
temperature
