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Equilibrium
When the rates of the forward and reverse reactions are equal.
Chemical Equilibrium
The identity of the substance changes, and sometimes the state does as well.
Chemical Equilibrium Example
Physical Equilibrium
ONLY the state of the substance changes.
Physical Equilibrium Example
Mass Action Expression (MAE) is also known asâŠ
The Equilibrium Constant / The Kc
The Mass Action Expression (MAE) showsâŠ
the relationship between the concentrations of the reactants and products in a chemical equilibrium.
Kc = Kp ONLY whenâŠ
În = 0
Kp Equation
Kp = Kc(RT)În
A Small Kc indicatesâŠ
That the reaction favors the reactants.
A Large Kc indicatesâŠ
That the reaction favors the products.
A homogeneous equilibrium involves a reaction where all substances are in _____ phase.
the same
A heterogeneous equilibrium involves a reaction where all substances are in ________ phases.
different
When finding Kc, we express the concentrations of Aqueous Solutions and Gases, but NOTâŠ
Pure Solids & Pure Liquids
If the reaction is multiplied by [a factor], the Original Kc isâŠ
raised to the power of [the factor].
When looking at the reverse reaction, you find the _____ of the Kc.
reciprocal (1/Kc)
If there are multiple reactions with Kcs, the net reaction Kc is found byâŠ
Multiplying all the Kcs.
Concentrations in MAE Units
mol/L
Gases in MAE Units
atm
____ and ____ are considered unitless quantities.
Kp and Kc
Stoichiometric coefficients affectâŠ
the MAE.
When you donât know whether or not the reaction is at equilibrium, you find theâŠ
Qc
Qc < Kc
The reaction needs to proceed towards products.
Qc > Kc
The reaction needs to proceed towards reactants.
Qc = Kc
The reaction is at equilibrium.
Le ChĂątelierâs Principle
If an external stress is applied to a system at equilibrium, the system will adjust to offset the stress and reach a new equilibrium.
Factors that AFFECT Equilibrium
Concentration, Volume & Pressure, Temperature, Catalysts
Factors that SHIFT Equilibrium
Concentration, Volume & Pressure, Temperature
Concentration of Products INCREASES
Shift Left â
Concentration of Products DECREASES
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Concentration of Reactants DECREASES
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Concentration of Reactants INCREASES
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Pressure INCREASES
Shift to the side with LEAST moles
Pressure DECREASES
Shift to the side with MOST moles
Volume INCREASES
Shift to the side with MOST moles
Volume DECREASES
Shift to the side with LEAST moles
Does a Catalyst shift Equilibrium?
No
Catalysts lower theâŠ
Ea
Temperature INCREASES in an Exothermic Reaction
Shift Left â
Temperature DECREASES in an Exothermic Reaction
Shift Right â
Temperature INCREASES in an Endothermic Reaction
Shift Right â
Temperature DECREASES in an Endothermic Reaction
Shift Left â
Note
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