Reversible Reactions (+ Energy Changes) & Equilibrium & Le Chatelier's Principle

What is a reversible reaction?

A reaction in which the products can react to produce the original reactants.

What do the two arrows mean?

The reaction can occur in both the forward and reverse directions.

How can the direction of a reversible reaction be changed?

By changing the conditions.

If the forward reaction is exothermic, what is the reverse reaction?

Endothermic.

If the forward reaction is endothermic, what is the reverse reaction?

Exothermic.

How do their energy transfers compare?

The same amount of energy is transferred in each direction, but in opposite directions.

What is equilibrium?

In a closed system, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate.

What is a closed system?

A system in which reactants and products cannot escape.

Do reactions stop at equilibrium?

No. Both forward and reverse reactions continue, but at the same rate.

Are the amounts of reactants and products necessarily equal at equilibrium?

No. Their amounts remain constant, but they do not have to be equal.

What happens when conditions are changed in a system at equilibrium?

The system responds to counteract the change until equilibrium is reached again.

What three changes can shift the position of equilibrium?

Changes in: concentration -- temperature -- pressure (for gaseous reactions).