Name ___________________________________________
Period _________
Average Atomic Mass Worksheet
1.
Isotope Name
Silver-107
Silver-109
Isotope Molar Mass
(g/mol)
106.90509
108.90470
Percentage
51.86
remainder
A. Find the missing percentage in the table.
B. Find the average atomic mass (g/mol) of an atom of silver.
2.
Isotope Name
Silicon-28
Silicon-29
Silicon-30
Isotope Mass (g/mol)
27.98
28.98
29.97
Isotope Abundance
92.21%
4.70%
3.09%
A. Silicon has three naturally occurring isotopes. Look over the data before you
begin the problem. Estimate the value of the answer before you begin the
calculation. Will the weighted average be closer to 28, 29, or 30?
B. Now, find the average atomic mass of an atom of silicon.
3.
Isotope Name
Iron-54
Iron-56
Iron-57
Iron-58
Isotope Abundance
5.9 %
91.72 %
2.10 %
0.280 %
Isotope Mass (g/mol)
53.94
55.93
56.94
57.93
A. Estimate the average atomic mass of iron.
B. Calculate the average atomic mass of iron.
4. Titanium has five common Isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%),
49
Ti (5.5%), 50Ti (5.3%). What is the average atomic mass of titanium?
ANALOGY Your chemistry grade is a weighted average. Tests are worth 60.0 %, labs
are worth 20.0 %, and homework is worth 20.0 %. Suppose for this semester, your
scores are: test average is 85.0 %, lab average is 77.0 %, and homework is 91.0 %.
A. What is your weighted average grade?