Equilibrium

Dynamic Equilibrium

Reactions can go backwards as well as forwards.

A system reaches ‘equilibrium’ when the rate of the forward

reaction equals the rate of the backward reaction.

e.g. CH3COOH + HOCH3 ⇌ CH3COOCH3 + H2O

In a closed system (one which is sealed), a reversible reaction is said

to be at dynamic equilibrium when:

Rate of the forward reaction =

Rate of the reverse reaction

Rules for dynamic equilibrium:

The concentration of reactants and products remains constant

The concentrations are not usually equal

The reaction has not stopped

A bottle of lemonade in a closed

system as the lid is on.

A bottle of lemonade in an open

system as the lid is off.

Equilibrium

At this point there is no more change in the quantities of

reactants and products.

Equilibrium is not necessarily at 50% reactants and 50%

products – it can be shifted nearer P or R.

A reversible reaction will remain at equilibrium forever unless the

reaction conditions are altered.

If a chemical system at equilibrium experiences a change in

concentration, temperature, or total pressure, then the equilibrium

shifts to counter-act the imposed change.

Example

A +

B

C

More products (C) are produced

Rules:

If equilibrium moves to the right;

If equilibrium moves to the left;

More reactants (A,B) are produced

Altering the Position of Equilibrium

If a chemical system at equilibrium experiences a change in

concentration, temperature, volume, or total pressure, then the

equilibrium shifts to counter-act the imposed change.

Le Chatelier’s Principle

If you’ve got an equilibrium reaction and you change the conditions,

the equilibrium will shift to try to cancel out what you’ve done.

You do something.

It does the opposite.

A reversible reaction will remain at equilibrium forever unless the

reaction conditions are altered.

If a chemical system at equilibrium experiences a change in

concentration, temperature, or total pressure, then the equilibrium

shifts to counter-act the imposed change.

Example

A +

B

C

More products (C) are produced

Rules:

If equilibrium moves to the right;

If equilibrium moves to the left;

More reactants (A,B) are produced

Altering the Position of Equilibrium

If a chemical system at equilibrium experiences a change in

concentration, temperature, volume, or total pressure, then the

equilibrium shifts to counter-act the imposed change.

Le Chatelier’s Principle

If you’ve got an equilibrium reaction and you change the conditions,

the equilibrium will shift to try to cancel out what you’ve done.

You do something.

It does the opposite.

A reversible reaction will remain at equilibrium forever unless the

reaction conditions are altered.

If a chemical system at equilibrium experiences a change in

concentration, temperature, or total pressure, then the equilibrium

shifts to counter-act the imposed change.

Example

A +

B

C

More products (C) are produced

Rules:

If equilibrium moves to the right;

If equilibrium moves to the left;

More reactants (A,B) are produced

Altering the Position of Equilibrium

If a chemical system at equilibrium experiences a change in

concentration, temperature, volume, or total pressure, then the

equilibrium shifts to counter-act the imposed change.

Le Chatelier’s Principle

If you’ve got an equilibrium reaction and you change the conditions,

the equilibrium will shift to try to cancel out what you’ve done.

You do something.

It does the opposite.

A reversible reaction will remain at equilibrium forever unless the

reaction conditions are altered.

If a chemical system at equilibrium experiences a change in

concentration, temperature, or total pressure, then the equilibrium

shifts to counter-act the imposed change.

Example

A +

B

C

More products (C) are produced

Rules:

If equilibrium moves to the right;

If equilibrium moves to the left;

More reactants (A,B) are produced

Altering the Position of Equilibrium

If a chemical system at equilibrium experiences a change in

concentration, temperature, volume, or total pressure, then the

equilibrium shifts to counter-act the imposed change.

Le Chatelier’s Principle

If you’ve got an equilibrium reaction and you change the conditions,

the equilibrium will shift to try to cancel out what you’ve done.

You do something.

It does the opposite.

A reversible reaction will remain at equilibrium forever unless the

reaction conditions are altered.

If a chemical system at equilibrium experiences a change in

concentration, temperature, or total pressure, then the equilibrium

shifts to counter-act the imposed change.

Example

A +

B

C

More products (C) are produced

Rules:

If equilibrium moves to the right;

If equilibrium moves to the left;

More reactants (A,B) are produced

Altering the Position of Equilibrium

If a chemical system at equilibrium experiences a change in

concentration, temperature, volume, or total pressure, then the

equilibrium shifts to counter-act the imposed change.

Le Chatelier’s Principle

If you’ve got an equilibrium reaction and you change the conditions,

the equilibrium will shift to try to cancel out what you’ve done.

You do something.

It does the opposite.

A reversible reaction will remain at equilibrium forever unless the

reaction conditions are altered.

If a chemical system at equilibrium experiences a change in

concentration, temperature, or total pressure, then the equilibrium

shifts to counter-act the imposed change.

Example

A +

B

C

More products (C) are produced

Rules:

If equilibrium moves to the right;

If equilibrium moves to the left;

More reactants (A,B) are produced

Altering the Position of Equilibrium

If a chemical system at equilibrium experiences a change in

concentration, temperature, volume, or total pressure, then the

equilibrium shifts to counter-act the imposed change.

Le Chatelier’s Principle

If you’ve got an equilibrium reaction and you change the conditions,

the equilibrium will shift to try to cancel out what you’ve done.

You do something.

It does the opposite.