IB Chemistry Unit 14 - Chemical Equilibrium

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 as…

The Equilibrium Constant / The K_c

The Mass Action Expression (MAE) shows…

the relationship between the concentrations of the reactants and products in a chemical equilibrium.

K_c = K_p ONLY when…

Δn = 0

K_p Equation

K_p = K_c(RT)^Δn

A Small K_c indicates…

That the reaction favors the reactants.

A Large K_c indicates…

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 K_c, we express the concentrations of Aqueous Solutions and Gases, but NOT…

Pure Solids & Pure Liquids

If the reaction is multiplied by [a factor], the Original K_c is…

raised to the power of [the factor].

When looking at the reverse reaction, you find the _____ of the K_c.

reciprocal (1/K_c)

If there are multiple reactions with K_cs, the net reaction K_c is found by…

Multiplying all the K_cs.

Concentrations in MAE Units

mol/L

Gases in MAE Units

atm

____ and ____ are considered unitless quantities.

K_p and K_c

Stoichiometric coefficients affect…

the MAE.

When you don’t know whether or not the reaction is at equilibrium, you find the…

Q_c

Q_c < K_c

The reaction needs to proceed towards products.

Q_c > K_c

The reaction needs to proceed towards reactants.

Q_c = K_c

The reaction is at equilibrium.

Le Châtelier’s 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

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Concentration of Products DECREASES

Shift Right →

Concentration of Reactants DECREASES

Shift Left ←

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 the…

E_a

Temperature INCREASES in an Exothermic Reaction

Shift Left ←

Temperature DECREASES in an Exothermic Reaction

Shift Right →

Temperature INCREASES in an Endothermic Reaction

Shift Right →

Temperature DECREASES in an Endothermic Reaction

Shift Left ←