Molarity in stoichiometry: Figuring out how much you need

The usefulness of the molarity concentration unit is readily apparent when dealing with reaction stoichiometry. For example, suppose that you want to know how many milliliters of 2.50 M sulfuric acid it takes to neutralize a solution containing 100.0 grams of sodium hydroxide. The first thing you must do is write the balanced chemical equation for the reaction:

H₂SO₄(aq) + 2 NaOH(aq) → 2 H₂O(l) + Na₂SO₄(aq)

You know that you have to neutralize 100.0 grams of NaOH. You can convert the weight to moles (using the formula weight of NaOH, 40.00 g/mol) and then convert from moles of NaOH to moles of H₂SO₄. Then you can use the molarity of the acid solution to get the volume:

It takes 500.0 milliliters of the 2.50 M H₂SO₄ solution to completely react with the solution that contains 100 grams of NaOH.