Chemical Equilibria

Le Châteliers Principle

Le Châteliers Principle

________: when a chemical system at equilibrium is disturbed, it returns to equilibrium by counteracting the disturbance.

Solids

________ are always omitted from the expressions for Q and K.

K

An increase in temperature will change K. It will increase ________ for an endothermic, and decrease ________ for an exothermic.

chemical equilibrium

If a(n) ________ is disturbed by adding a reactant or product, the system will proceed in the direction that consumes part of the added species.

Qc

________ can be calculated at any point in a reaction.

Homogenous equilibrium

________: one in which all of the reactants and products are present in the same phase.

Heterogenous equilibria

________: contain reactants and products that are in two or more different phases.

concentration of products

The value of Qc depends on the ________ and reactants present at that particular moment.

Equilibrium constant

________ (K): the value of Q when the reaction is at equilibrium.

reversible reactions

For ________, catalysts increase the rates of the forward and ________.

gas phase solutions

For ________, the equilibrium constant may be expressed in terms of either the molar concentrations (Kc) or partial pressures (Kp) of the reactants and products.

SOLID

If what is added or removed is a(n) ________ or liquid, the reaction does not shift at all.

K

If ________ is very small, the mixture contains mostly reactants at equilibrium.

Equilibrium constant (K)

the value of Q when the reaction is at equilibrium

When Q < K*

• reaction must shift FORWARD

When Q > K*

• reaction must shift BACKWARD

When Q = K*

• reaction is at equilibrium, and will maintain constant concentration

Homogenous equilibrium

one in which all of the reactants and products are present in the same phase

Heterogenous equilibria

contain reactants and products that are in two or more different phases

Le Châteliers Principle

when a chemical system at equilibrium is disturbed, it returns to equilibrium by counteracting the disturbance

Result

A catalyst causes the system to reach equilibrium more quickly