Kc and Le Chatelier's Principle Flashcards
What is the definition of dynamic equilibrium
•dynamic: the rate of forwards reaction= the rate of backwards reaction
•equilibrium: the concentrations of products and reactants are constant
How is dynamic equilibrium reached? (3m)
•at the start, the forwards reaction is fast and the backwards reaction is slow
•after the start, the forwards reaction slows and the backwards reaction speeds up
•the rates become equal
What is a closed system
Carried out in a sealed container
Why are closed systems used
So no products escape
On equilibrium graphs, where I’d dynamic equilibrium reached
When the reactants and products are constant
(Both straight horizontal lines)
Which way does equilibrium shift for products and reactants to “cross” on the graph
To the right
Which way does equilibrium shift for products and reactants to never meet on the graph
To the left
State Le Chateliers principle
The position of equilibrium will always shift to oppose any changes made to it
What can affect position of equilibrium
•concentration
•temperature
•pressure
Which way does equilibrium shift when conc of reactants increases
To the right
To oppose increase in concentration
How is yield of products affected when conc of reactants increases and why
Equilibrium shifts to the right to oppose conc increase
Yield increases
Which way does equilibrium shift when pressure increases
2reactants –> 1product
Fewer moles on right
Equilibrium shifts to the right to oppose pressure increase
When can pressure affect equilibrium
Gaseous
Which way does equilibrium shift when pressure increases
3reactants –> 3products
No change
If reaction is endothermic, which way does equilibrium shift when temperature increases
Forwards reaction is endothermic
Equilibrium shifts to the right to oppose increase in temperature
What is a catalyst
Speeds up the rate of reaction
By providing an alternate reaction pathway
With a lower activation energy
How does a catalyst work when added to equilibrium
•forwards and backwards reaction increase equally
•no change in position to equilibrium
•dynamic equilibrium is reached faster
What are the ideal conditions of the harder process
400atm
350°c
Why are ideal conditions of the harder process not used in the industry
High pressure is too expensive
What are the compromised conditions of the harder process
200atm
450°c
What catalyst is used in the harber process
Iron
What is the formula for Kc
[Products]/ [reactants]
When Kc>1 equilibrium shifts to the…
Right
When Kc<1 equilibrium shifts to the…
Left
What happens when your units cancel out when calculating Kc
NO UNITS
What must you always consider when calculating Kc
If moles are in equilibrium
(Use an ice box)
When do you not need to calculate concentration
Number of reactions=number of products
Volumes cancel out
