The number in front of each molecule in a chemical equation is called a coefficient. Coefficients are used to indicate the quantity of each substance involved in a chemical reaction. For instance, in the equation 2H2 + O2 → 2H2O, the coefficient ‘2’ in front of H2 and H2O shows that there are two molecules of hydrogen gas and two molecules of water produced in the reaction.
Coefficients help balance chemical equations, ensuring that the law of conservation of mass is upheld. This law states that matter cannot be created or destroyed in a chemical reaction, meaning the number of atoms for each element must be the same on both sides of the equation. By adjusting the coefficients, chemists can accurately represent how many molecules react and how many products are formed.