GENERAL EQUILIBRIUM Flashcards
Chemical Equilibrium
the concentrations of all reactants and products remain constant with time
The equilibrium of a reaction is determined by:
- Initial Concentration
- Relative Energies of the reactants and products
- Relative degree of “organization” or “orientation” of the reactants and products
What is dynamic equilibrium
The forward reaction = the reverse reaction
What is true about the initial rate of forward and reverse reaction in a system where only reactants are present?
Reactants are forming faster than products
What is true about the rates of forward and reverse reactions at equilibrium?
They are the same
Why does equilibrium occur?
nature demands balance (Think bonnie from TVD)
The Law of Mass Action
expresses the relationship between the concentrations of the reactants and products at equilibrium in any reaction
Equilibrium Constant K
the ratio of the forward reaction to the reverse reaction
DOES NOT INCLUDE PURE SOLIDS AND PURE LIQUIDS
The equilibrium expression
is the RECIPROCAL of the given reaction
* PRODUCTS OVER REACTANTS**
IF YOU REVERSE AN EQUATION:
YOU MUST TAKE THE RECIPROCAL OF K: 1/K
When the balanced equation for a reaction is multiplied by a factor
the equilibrium expression K for the new reaction is the original expression raised the power of that factor
The units of K are:
Dimensionless because the units cancel out
R =
0.0821 L x atm / K x mol
IF K = 1
THE REACTION IS AT EQUILIBRIUM
IF K > 1
THE REACTION SHIFTS RIGHT AND PRODUCTS ARE FAVORED AT EQUILIBRIUM
IF K < 1
THE REACTION SHIFTS LEFT AND THE REACTANTS ARE FAVORED AT EQUILIBRIUM
K < Q < 1
GOES LEFT
K = Q = 1
EQUILIBRIUM
K > Q > 1
GOES RIGHT
BIG K
OVER 100
LITTLE K
UNDER .01
LeChatelier’s Principle
a change in one of the variables that describe a system at equilibrium produces a shift in the position of the equilibrium the counteracts the effect of the change,
Change in concentration
shift to the opposite side
Increase in reactant
shift to make product
increase in product
shift to make more reactant
decrease reactant
shift to make more reactant
decrease in product
shift to make more product
Change in Pressure
only affects systems having gaseous products and/or reactants
increase pressure
shift to side with fewer gas moles
decrease pressure
shift to side with more gas moles
If same number of moles of gas
changes in pressure does not affect equilibrium
Adding inert gas (noble gases)
does not affect equilibrium because the partial pressures of the other gases are not changed. Total pressure increases but individual partial pressures do not change
Change in temperature
WATCH WHERE YOU PUT DELTA H IN AN EQUATION!
An increase in temp, affects reactions in two different way
EXOTHERMIC: shifts left to reactants
ENDOTHERMIC: shifts right to products
A decrease in temp
ENDOTHERMIC: SHIFTS LEFT
EXOTHERMIC: SHIFTS RIGHT
ADDING A CATALYST
does not affect anything
just makes the reaction occur faster
Increase in volume
shifts right to products
