What indicates how much molar mass of each reactant will be used up in a reaction?

The molar mass of each reactant in a chemical reaction indicates the amount of each substance that will be consumed based on the stoichiometric coefficients in the balanced chemical equation. By using these coefficients, one can determine the mole ratio between reactants and products, allowing for calculations of how much of each reactant is required for a complete reaction. The actual amount used depends on the initial quantities and the limiting reactant, which is the reactant that will be completely consumed first.