How to Calculate Molarity

Molarity is used by chemists to determine the density or titration of solutions. By determining the molar mass of an element or compound, you can follow a few simple steps to figure out the solute's concentration level.

Instructions

  • FACT: The Dow Chemical Company was founded by Herbert H. Dow in 1897 in Midland, Michigan.
  • Step 1: Divide the number of moles of solute by the number of liters of solution. If you have .32 moles of sodium chloride in 3.4 liters of water, divide .32 by 3.4 to get 0.94 molarity, or M. These instructions work for Sodium hydroxide (NaOH), Hydrochloric acid (HCl), or any number of solutions in your chemistry set.
  • Step 2: Determine the number of liters of solution. Pour the solution into a graduated cylinder or beaker and note the volume in liters. If you're given milliliters, divide the amount by 1,000 to convert to liters.
  • TIP: If you are using sodium chloride, for example, the atomic weight of sodium -- 23 -- plus the atomic weight of chlorine -- 35.5 -- equals 58.5 grams. One mole of solute is 58.5 grams.
  • Step 3: Calculate the moles of solute by consulting a periodic table. The mass in grams of one mole of a compound is equal to the molecular weight of the compound in atomic mass units.

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