In a balanced chemical equation, the coefficient indicates the number of molecules.

• A. Subscripts
• B. Moles
• C. Coefficient
• D. Molarity

Answer: (C)

In a balanced chemical equation, the coefficient is the scaling factor that shows how many molecules (or, equivalently, moles) of each substance are involved in the reaction. It sets the relative amounts of reactants and products so the total number of atoms of each element is the same on both sides. For example, in 2 H2 + O2 → 2 H2O, the coefficients tell you that two molecules of hydrogen gas react with one molecule of oxygen gas to produce two molecules of water. Subscripts are about the composition of a single molecule (how many atoms of each element are in that molecule), not how much you have overall, which is why they don’t indicate amounts. Molarity is a measure of concentration (moles per liter) and isn’t part of balancing the equation.