1 mole Ag
107.87 grams Ag
1870 grams Ag
1
×
1 mole Ag
107.87 grams Ag
17.3 mole Ag
201 grams Hg
1 mole Hg
0.004 moles Hg
1
×201 grams Hg
1 mole Hg
0.8 grams Hg
CHARACTERISTICS OF ATOMS
DOE-HDBK-1015/1-93
Fundamentals of Chemistry
CH-01
Rev. 0
Page 10
Example 1:
A silver bar has a mass of 1870 grams. How many moles of silver are in the bar?
Solution:
Since the atomic mass of silver (Ag) is 107.87 amu, one mole of silver has a mass o
f
107.87 grams. Therefore, there is one mole of Ag per 107.87 grams of Ag or
. There are 1870 grams of silver.
Example 2:
Mercury (Hg) is the only metal that exists as a liquid at room temperature. It isused in
thermometers. A thermometer contains 0.004 moles of mercury. How many grams of
mercury are in the thermometer?
Solution:
Since the atomic mass of Hg is 201 amu, one mole of Hg has a mass of 201 grams of Hg
or
. There are 0.004 moles of Hg.
Mole of Molecules
The mass of a mole of molecules ofa substance is the molecular mass expressed in grams. For
example, an oxygen molecule (O) has a molecular mass equivalent to 32.0 grams because each
2
oxygen atom has a molecular mass of 16.0 grams. (Recall that to obtain the molecular mass, the
atomic masses of all atoms that appear in the formula are added.) If the atomic masses of the
carbon and four hydrogen atoms in methane, CH , are added, the total is 16 amu. Therefore, one
4
mole of CH has a mass of 16 grams. The mass of a mole of molecules is called the molar mass
4
or gram molecular weight(GMW).
