SECTION SUMMARY
10.2
Mole-Mass and Mole-Volume Relationships Summary:
The molar mass of an element or compound is the conversion factor for converting
between the mass and the number of moles of a substance.
For example, there are 18 grams in one mole of water molecules. People can easily
use the molar mass (18 g/mol) to calculate the mass of some moles of water
molecules or the number of moles of some grams of water.
36 gofwater 
1moleofwater
 2molesofwater
18 gofwater
4molesofwatermolecule s 
Mass  mole
18 gofwater
 72 gofwater
1moleofwatermolecule
Mole  mass
One mole of any gas occupies a volume of 22.4 L at standard temperature and
pressure. One mole of any substance contains Avogadro’s number of particle, so 22.4
L of any gas at STP contains 6.02 x 1023 representative particles of that gas.
At standard temperature and pressure, one mole of any gas occupies a volume of
22.4L. This quantity is known as the molar volume of the gas. To determine the
22.4 L
volume in liters of 2.00 mol of SO2 gas at STP, you would use
as a conversion
1mol
factor. Density, expressed in the units g/L, is used as a conversion factor when
converting from volume to molar mass. When converting between number of
representative particles, masses, and volumes, you must always convert to mole as an
intermediate step.
10.2
Mass-Mole and Mole-Volume Relationships Vocabulary Terms:
Avogadro’s hypothesis: equal volumes of gases at the same temperature and
pressure contain equal numbers of particles
Avogadro’s number:
the number of representative particles in a mole
Standard temperature: 0oC
Molar mass:
the mass (in grams) of one mole of a substance
Molar volume
22.4 L of a gas at STP
STP
standard temperature (0oC) and pressure (101.3 kPa or 1.0
atm)
The End of the Summary