A chemical equation, or reaction equation, expresses the stoichiometric relationship between the reactants, written to the left of the arrow, and the products, written to the right. It uses chemical formulas together with coefficients to show both what is involved and in what proportions. A correctly balanced equation has equal numbers of each kind of atom on both sides, reflecting the conservation of mass.

化学方程式(反应方程式)表示写在箭头左侧的反应物与写在箭头右侧的生成物之间的化学计量关系。它用化学式连同系数来表明参与反应的物质及其比例。配平正确的方程式两侧每种原子的数目相等,体现了质量守恒。