5.6.2 Reversible reactions and dynamic equilibrium

reversible reaction

a chemical reaction in which the products re-form the original reactants

What can cause a reversible reaction to change direction?

Change in conditions eg: Heat/cool

What happens as the reactants react?

their concentration falls so the forward reaction will slow down

What happens when more product is made?

The reverse reaction begins speeding up

What happens when the forward reaction is going at the same speed as the reverse reaction?

It is at equilibrium

What is equilibrium?

Equilibrium is reached when the reactions occur at exactly the same rate in both directions

Where does equilibrium only occur?

In a closed system

True or false: Equilibrium is where the amount of reactants and products are equal?

False - equilibrium can lie to the left or the right

What is grater if equilibrium lies to the left?

reactants

What is grater if equilibrium lies to the right?

products

What factors can effect equilibrium:

- Temperature
- Pressure (only for gases)
- concentration of reactants and products

What is the reverse reaction if the forward reaction is exothermic

endothermic

Is the amount of energy transferred from the environment in the endothermic reaction equal to the energy transferred in the exothermic reaction

Yes

Le Chatelier's Principle

States that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress.

What happens if temperature is increased in a reaction at equilibrium?

* The products in the endothermic reaction increase.
* The products in the exothermic reaction decrease

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This can be reversed for a decrease in temperature.

What happens if pressure is increased in a reaction at equilibrium?

an increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules as shown by the symbol equation for that reaction

What happens if pressure is decreased in a reaction at equilibrium?

a decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction.

What happens if concentration is changed in a reaction at equilibrium?

If the concentration of one of the reactants or products is changed, the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again.

What happens if concentration of reactants is increased in a reaction at equilibrium?

more products will be formed until equilibrium is reached again.

What happens if concentration of products is decreased in a reaction at equilibrium?

More reactants will react until equilibrium is reached again.