In a chemical equation, what is the purpose of the coefficients?

Coefficients in a chemical equation serve to indicate the relative number of moles of each substance involved in the reaction. They provide a clear quantitative relationship between the reactants and products, allowing us to understand how many molecules or moles of each substance are needed or produced during the reaction. For instance, in the equation 2H₂ + O₂ → 2H₂O, the coefficient '2' before H₂ and H₂O means that two molecules of hydrogen gas react with one molecule of oxygen gas to produce two molecules of water.

This concept is essential for balancing chemical equations, as it ensures that the law of conservation of mass is upheld—meaning the total number of atoms of each element must be the same on both sides of the equation. Understanding coefficients aids chemists and operators in performing calculations related to reaction yields, reactant quantities, and stoichiometry.