Chemical equation - Definition and Overview

In chemistry, a chemical equation is a symbolic representation of a chemical reaction. For example, the combustion of methane in oxygen is

CH₄ + 2 O₂ → CO₂ + 2 H₂O,

and the reversible reaction of the Haber process is

N_2(g) + 3H_2(g) ↔ 2NH_3(g) + ΔH.

How do you read chemical equations?

The first number in a set such as 3H₂O tells how many molecules of the substance there is. The number in subtext following the element tells how many atoms of the element there are. The letters represent elements from the Periodic table.

ex. 3H₂O means 3 molecules, each containing 2 parts Hydrogen, 1 part Oxygen. See also full equation and ionic equation.