molarity (M)
moles of solute (n)
liters of solution (V)
1 atom of Na
22.989 amu
1 atom of Cl
35.453 amu
1 molecule of NaCl
58.442 amu
Fundamentals of Chemistry
DOE-HDBK-1015/1-93
CHEMICAL EQUATIONS
Rev. 0
CH-01
Page 37
Density
Density is 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 with
size but density will remain constant. Temperature will affect the density of a substance and
the temperature at which density for that substance was determined is usually reported along
with the density value.
Molarity
A useful way to express exact concentrations of solutions is molarity. Molarity is defined as
moles of solute per liter of solution. Molarity is symbolized by the capital letter M. It can be
expressed mathematically as follows.
Notice that the moles of solute are divided by the liters of solution not solvent. One liter of one
molar solution will consist of one mole of solute plus enough solvent to make a final volume
of one liter.
Example 1:
Prepare one molar solution of NaCl.
Solution:
a)
Calculate the molecular weight of the salt
One 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 the
solution to one liter.
