Chemistry Isotopes Solution: There are two stable isotopes of bromine. Their ma...

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# Solution: There are two stable isotopes of bromine. Their masses are 78.9183 and 80.9163 amu. If the average atomic mass of bromine is 79.9091 amu, what is the natural abundance of the heavier isotope? The percent abundance of  81Br:

Problem

There are two stable isotopes of bromine. Their masses are 78.9183 and 80.9163 amu. If the average atomic mass of bromine is 79.9091 amu, what is the natural abundance of the heavier isotope?

The percent abundance of  81Br:

Solution

We’re being asked to calculate the percent abundance of bromine-81 (81Br).

We can use the following equation:

where:

atomic mass = average atomic mass of the element

f.a. = fractional abundance of the isotope

To get f.a., we simply need to divide the given percent abundance by 100.

We’re given the following values:

Average Atomic Mass = 79.9091 amu

Bromine-81: Mass = 80.9163 amu

Bromine-79: Mass = 78.9183 amu View Complete Written Solution