Reversible Reactions

In some chemical reactions, the products of the reaction can react with each other to re-form the original reactants. These reactions are called reversible reactions.

Reversible reactions are ones which happen in both directions at the same time. Reversible reactions can be represented in the following way:

A + B ⇌ C + D

Reversible reactions are shown using a double headed arrow ⇌ one pointing in each direction.

If a reversible reaction is exothermic in one direction it is endothermic in the other direction.

When a reversible reaction takes place in a closed container, an equilibrium will be reached. This means that the forward and the backward reactions have the same rate of reaction.

If the conditions are changed then the position of equilibrium will move to counteract the change.

If we increased the temperature of a reaction at equilibrium, the position of equilibrium moves in the endothermic direction to reduce the temperature.

If the pressure is increased, the position of equilibrium shifts towards the side with the smaller number of molecules.