A coefficient in a chemical equation refers to the large number that appears before a compound or element to balance the equation. It indicates the relative number of molecules or moles of each reactant and product involved in a chemical reaction. Coefficients are used to ensure that the law of conservation of mass is obeyed, meaning that the total number of atoms of each element remains the same on both sides of the equation.
For example, in the balanced chemical equation:
2H₂ + O₂ → 2H₂O
The coefficient "2" in front of H₂ and H₂O indicates that two molecules of hydrogen gas (H₂) react with one molecule of oxygen gas (O₂) to produce two molecules of water (H₂O). The coefficients play a crucial role in maintaining the balance of atoms before and after the reaction.