The molarity is the number of moles of solute in 1 liter of solution.  One molar (1 M) of a solution has 1 mole of solute in every 1 liter of solution.  There are 6.022 * 10 ²³ molecules in one mole.  If the volumes of a solution are the same, then they have the same number of molecules.  Molarity is useful because it tells you how many moles are in every liter.  The formula for finding molarity is:

moles solute = (molar concentration of solution) * (Volume in Liters)

            The molality is the number of moles of solute dissolved in one kilogram of solvent.  One molal is written by 1 m.  A little �m� is represented, whereas in molarity, a big �M� is written.  The formula for finding molality is:

molality = moles of solute

                         kilograms of solvent

(Dorin 349-352)