Final answer:
A chemical equation is balanced by ensuring the same number of each type of atoms on both sides, which may require different numbers of reactant and product particles. Coefficients are adjusted without changing the chemical identities, to satisfy the law of conservation of matter.
Step-by-step explanation:
An equation can be balanced even if the number of reactant particles differs from the number of product particles because the balancing is based on the total number of each type of atoms on both sides of the reaction, not the number of molecules. As per the law of conservation of matter, atoms are not created or destroyed in a chemical reaction. Hence, the same number of each type of atom must be present on both sides of a balanced equation. Coefficients are used in front of the reactants or products to ensure that the number of atoms is conserved from the reactants to the products.
For example, when balancing the equation for the formation of water from hydrogen and oxygen, the equation can start as H₂ + O₂ → H₂O. Initially, this equation is not balanced because there are two oxygen atoms on the reactant side but only one on the product side. By adding a coefficient of 2 in front of H₂O, the equation becomes balanced as H₂ + O₂ → 2 H₂O, with two hydrogen atoms and two oxygen atoms on each side.