Balance the chemical equation

Explanation

Let us start by simply writing a chemical equation in terms of the formulas of the substances, remembering that both elemental hydrogen and chlorine are diatomic:

H₂ + Cl₂ → HCl

There are two hydrogen atoms and two chlorine atoms in the reactants and one of each atom in the product. We can fix this by including the coefficient 2 on the product side:

H₂ + Cl₂ → 2HCl

Now there are two hydrogen atoms and two chlorine atoms on both sides of the chemical equation, so it is balanced.