molarity (M)moles of solute (n)liters of solution (V)1 atom of Na22.989 amu1 atom of Cl35.453 amu1 molecule of NaCl58.442 amuFundamentals of ChemistryDOE-HDBK-1015/1-93CHEMICAL EQUATIONSRev. 0CH-01Page 37DensityDensityis the measure of the mass per unit volume of a material (density = mass/volume).Density is a characteristic of a substance; mass and volume are not. Mass and volume vary withsize but density will remain constant. Temperature will affect the density of a substance andthe temperature at which density for that substance was determined is usually reported alongwith the density value.MolarityA useful way to express exact concentrations of solutions is molarity. Molarity is defined asmoles of solute per liter of solution. Molarity is symbolized by the capital letter M. It can beexpressed mathematically as follows.Notice that the moles of solute are divided by the liters of solution not solvent. One liter of onemolar solution will consist of one mole of solute plus enough solvent to make a final volumeof one liter.Example 1: Prepare one molar solution of NaCl.Solution:a)Calculate the molecular weight of the saltOne mole is equal to the gram molecular weight, so one mole = 58.442 grams.b)58.442 grams of NaCl is weighed out and sufficient water is added to bring thesolution to one liter.
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