What is a chemical equation ?

During a chemical reaction, certain substances react together to form some new substances. A reaction is described in terms of the names and quantities of the reactants and products. For example, the chemical reaction during the burning of carbon (or coal) may be described by the statement, “carbon is burnt in excess of air (or oxygen) to produce carbon dioxide.” This reaction may also be described by a word equation, viz.,

Carbon + Oxygen (excess) → Carbon dioxide

Such word equations are long, and not convenient for describing chemical reactions. These long word equations can be shortened by using symbols and formulae of the substances involved in the reaction.

For example, the reaction of zinc metal with dilute sulphuric acid to produce zinc sulphate and hydrogen may be written as,

Zinc (metal) + dil. Sulphuric acid → Zinc sulphate + Hydrogen

This word equation may be written in terms of symbols and formulae as,

Zn + dil. H₂SO₄ → ZnSO₄ + H₂

Thus, Zn + dil. H₂SO₄ → ZnSO₄ + H₂ is the chemical equation for the reaction between zinc and sulphuric acid.