Lecture 5 Flashcards
What is equilibrium?
A state in which there are NO observable CHANGES over time.
What are the requirements for equilibrium?
CLOSED SYSTEM
CONSTANT TEMPERATURE and PRESSURE.
REVERSIBLE process/ reaction.
Rates of opposing changes are EQUAL.
What are the properties of equilibrium systems?
DYNAMIC, in constant motion.
REVERSIBLE
Approach from either DIRECTION.
Both REACTANTS and PRODUCTS present at ALL times.
When will a reaction reach dynamic equilibrium?
When the rate of the forwards reaction is equal to the rate of the backwards reaction.
What is the Reaction Quotient?
CONCENTRATION of products and reactants to each other at ANY POINT in a reaction.
Reaction Quotient equation:
Q= [C]c[D]d/ [A]a[B]b
[Products]/ [Reactants]
What is the equilibrium constant?
The value of the reaction quotient at EQUILIBRIUM.
What is Kc?
Concentration Equilibrium Constant.
What do you not include in Kc or Kp equations?
SOLVENTS or SOLIDS
What is a homogenous equilibria?
Reactants and products are in the SAME physical STATES.
What is a heterogeneous equilibria?
Reactants and products are in DIFFERENT physical STATES.
What does K allow us to do?
PREDICT how a reaction will PROGRESS to achieve equilibrium.
CALCULATE the CONCENTRATION of reactants and products at equilibrium.
If there is a small Kc (less than one) what does this tell us about the reaction?
Favours reactants.
Equilibrium lies to LHS.
Little reaction occurs.
If there is a large Kc, what does this tell us about the reaction?
Favours products.
Equilibrium lies to RHS.
Reaction nearly complete.
If Kc is less that one what does this tell an individual about ΔG? Why?
The reaction is not spontaneous.
The log of a number smaller than one will be a MINUS and a MINUS + MINUS is POSITIVE so ΔG is NOT SPONTANEOUS.
What is Le Chatelier’s principal?
“When a change is applied to a system in dynamic equilibrium, the system reacts to oppose the effect.”
What does Le chatelier’s principal mean?
- A system at equilibrium under STRESS will SHIFT to RELIEVE the stress.
- There will be a CHANGE in the rate of the forwards or reverse reaction to RETURN the system to equilibrium.
What is the only thing that can change the value of the equilibrium constant?
Temperature.
Why does temperature alter the equilibrium constant?
Altering the temperature affects both the forwards and backwards reaction but alters the two rates to DIFFERENT extents. Therefore the equilibrium moves producing a new equilibrium constant.
CONCENTRATION: What will happen to the reaction if you: Add reactant Remove reactant Add product Remove product
Forward
Back
Back
Forward
PRESSURE: What will happen to the reaction if you:
Increase
Decrease
Towards fewer moles of gas.
Towards more moles of gas.
For an endothermic reaction what happens when you:
Increase the temperature
Decrease the temperature
Forward K changes
Reverse K changes
For an exothermic reaction what happens when you:
Increase the temperature
Decrease the temperature
Reverse K changes
Forward K changes
What happens when you add a catalyst to an equilibrium reaction? Why?
Increases rate equally, but does not affect the position of equilibrium because the rate of both reactions is affected equally.
