Topic 2 Reversible and irreversible reactions

Some chemical reactions simply proceed in one direction until the reactants are used up. These reactions are known as irreversible.

Reagents→ Products

For example, a combustion reaction, in which methane reacts with oxygen in the air:

CH4 (gas) + 2O2(gas) →CO2 (gas) + 2H2O (gas)

However, other reactions are classified as reversible. In a reversible reaction, reactants become products, but also products become reactants.

Reagents ↔ Products

For example, the reaction of nitrogen and hydrogen to form ammonia:

3H2(gas)+N2 (gas)↔ 2NH3(gas)

Here is an example of a reversible reaction of glucose with oxygen in the air.