# Equilibrium and Le Chatelier's PrinciplePage 1

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Slide 1

Equilibrium and Le Chatelier’s Principle

Slide 2

CA Standards

Slide 3

## Chemical Equilibrium

Reversible Reactions:

A chemical reaction in which the products

can react to re-form the reactants

Chemical Equilibrium:

When the rate of the forward reaction

equals the rate of the reverse reaction

and the concentration of products and

reactants remains unchanged

2HgO(s)  2Hg(l) + O2(g)

Arrows going both directions (  ) indicates equilibrium in a chemical equation

Slide 4

## LeChatelier’s Principle

When a system at

equilibrium is placed under

stress, the system will

undergo a change in such

a way as to relieve that

stress.

Henry Le Chatelier

Slide 5

## Le Chatelier Translated:

When you take something away from a system at equilibrium, the system shifts in such a way as to replace what you’ve taken away.

When you add something to a system at equilibrium, the system shifts in such a way as to use up what you’ve added.

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## LeChatelier Example

#1

A closed container of ice and water at equilibrium. The temperature is raised.

Ice + Energy  Water

The equilibrium of the system shifts to the _ to use up the added energy.

right

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LeChatelier Example #2

A closed container of N2O4 and NO2 at equilibrium. NO2 is added to the container.

N2O4 (g) + Energy  2 NO2 (g)

The equilibrium of the system shifts to the _ to use up the added NO2.

left

Slide 8

LeChatelier Example #3

A closed container of water and its vapor at equilibrium. Vapor is removed from the system.

water + Energy  vapor

The equilibrium of the system shifts to the _ to replace the vapor.

right

Slide 9

LeChatelier Example #4

A closed container of N2O4 and NO2 at equilibrium. The pressure is increased.

N2O4 (g) + Energy  2 NO2 (g)

The equilibrium of the system shifts to the _ to lower the pressure, because there are fewer moles of gas on that side of the equation.

left