C6 Le Chatelier's Principle and Equilibrium

C6 Le Chatelier's Principle and Equilibrium

Keywords:

Equilibrium

Forward reaction

Backward reaction

Closed system

Reactants

Products

Multiple Choice

Where do you find the reactants in a chemical equation?

• Left hand side

• Right hand side

Open Ended

Magnesium + Oxygen = Magnesium Oxide

Name a reactant in the reaction above.

Open Ended

Magnesium + Oxygen = Magnesium Oxide

Name a product in the reaction above.

Reversible reactions go back and forth between reactants (left hand side) to products (right hand side).

Henry Louis

Le Chatelier

This man is called Le Chatelier.

In this photo he has little hair.

He came up with a principle,

That seemed very sensible,

And now we teach it every year!

Le Chatelier's Principle

If you change one condition when a reaction is at equilibrium, the system will resist the change!

You do something to a reaction, it will try to do the opposite to fight the change!

Multiple Choice

We say a reversible reaction is at equilibrium when the forward and backward reaction have ....................... rates.

• equal

• different

• faster

• slower

Equilibrium does not like change!

You increase temperature, it will go the 'cooler' route (endothermic).

You decrease temperature, it will go the 'warmer' route (exothermic).

Multiple Choice

Remember combustion from C7?

Combustion is an EXOTHERMIC reaction.

How could this reaction feel?

• Hot

• Cold

Multiple Choice

*Pause for thought*

A forward reaction is exothermic (warmer).

This means the backwards reaction is endothermic (cooler).

If you INCREASE temperature the reaction will want to do the opposite to resist the change.

Will equilibrium shift backwards (left) or forwards (right)?

• Forward (its going to make more product)

• Backwards (its going to make more reactant)

Multiple Choice

A forward reaction is exothermic (warmer).

This means the backwards reaction is endothermic (cooler).

If you DECREASE temperature the reaction will want to do the opposite to resist the change.

Will equilibrium shift backwards (left) or forwards (right)?

• Forward (its going to make more product)

• Backwards (its going to make more reactant)

Multiple Choice

A forward reaction is endothermic (cooler).

This means the backwards reaction is exothermic (warmer).

If you INCREASE temperature the reaction will want to do the opposite to resist the change.

Will equilibrium shift backwards (left) or forwards (right)?

• Forward (its going to make more product)

• Backwards (its going to make more reactant)

Photosynthesis is an endothermic reaction = it takes IN energy from it's surroundings.

Multiple Select

Equation for photosynthesis:

Carbon dioxide + Water = Glucose + Oxygen

Select the reactants in this reaction.

• Carbon dioxide

• Oxygen

• Water

• Glucose

Multiple Select

Equation for photosynthesis:

Carbon dioxide + Water = Glucose + Oxygen

Select the products in this reaction.

• Carbon dioxide

• Oxygen

• Water

• Glucose

Multiple Select

Equation for photosynthesis:

Carbon dioxide + Water = Glucose + Oxygen

Assuming this is a reversible reaction, when you increase temperature this reaction shifts to the right. What are making more of?

• Carbon dioxide

• Oxygen

• Water

• Glucose

Multiple Choice

Equation for photosynthesis:

Carbon dioxide + Water = Glucose + Oxygen

When you increase the concentration of water, this reaction shifts to the right. What are you making more of?

• Reactants (Carbon dioxide + Water)

• Products (Oxygen + Glucose)

Equilibrium does the opposite to what you do to the reaction.

If you INCREASE concentration of reactants, equilibrium will shift right to make more products!

Multiple Choice

You increase the concentration of reactants.

Where will equilibrium shift?

(Remember equilibrium does the opposite to you - to resist the change)

• Right (makes more products)

• Left (starts making more reactants)

Multiple Choice

You decrease the concentration of reactants.

Where will equilibrium shift?

(Remember equilibrium does the opposite to you - to resist the change)

• Right (makes more products)

• Left (starts making more reactants)

Multiple Choice

You increase the concentration of products.

Where will equilibrium shift?

(Remember equilibrium does the opposite to you - to resist the change)

• Right (makes more products)

• Left (starts making more reactants)

Lesson Summary

• Equilibrium is when rate of forward and reverse (backward) reaction is the same/ equal.

• Le Chatelier's Principle is the idea that if you change a condition, equilibrium will resist the change.

• Reversible reactions in equilibrium can shift left (make more reactants) or right (make more products)