# Average atomic mass worksheet by hedongchenchen

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```									                                           Chem 2202

1. Determine the average atomic mass for each of the following:

Isotope name     Percent abundance                    Average Atomic Mass
a.
carbon-12              98.9%

carbon-13              1.1%

carbon-14           1.0 x 10-10%

b.
oxygen-16             99.762

oxygen-17              0.038

oxygen-18               0.2

2. Calculate the average atomic mass of an element. For example, there are two isotopes of boron
(boron-10 and boron-11). What is the average atomic mass of boron if boron-10 has a
percent abundance of 19.88% while boron-11 has a percent abundance of 80.22%?

3. There are two naturally occurring isotopes of chlorine: chlorine-35 and chlorine-37. Determine
the average atomic mass of chlorine if the relative abundance of chlorine atoms in nature is
75% chlorine-35 and 25% chlorine-37?

4. The average atomic mass of hydrogen is 1.01. Which isotope of hydrogen do you think is most
abundant in nature? Why?

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