Final answer:
In a chemical reaction, numbers in front of a chemical formula indicate the number of molecules involved. These numbers, called coefficients, explain the mole ratio between reactants and products and are vital for balancing the chemical equation.
Step-by-step explanation:
Numbers in front of a chemical formula in a chemical reaction indicate how many molecules are involved. In a balanced chemical equation, these numbers are known as coefficients and they describe the mole ratio of the reactants and products. For instance, if we have a coefficient of 2 in front of H₂O (2H₂O), it signifies that two molecules, or two moles, of water are produced in the reaction.
The coefficients are essential for balancing chemical equations as they represent the relative amounts of each substance involved. Without coefficients, it is understood that only one molecule or mole of a substance is involved (e.g., O₂ and CO₂ are singular in the equation because they lack a preceding coefficient). It is important to note, a coefficient of 1 is typically omitted as it is implied.