We’re given the following values:
Average Atomic Mass = 10.821 amu (found in books or the internet)
Boron-10: Mass = 10.01294 amu
Boron-11: Mass = 11.00931 amu
We don’t know the percent abundance of boron but we can use the fact that the f.a. of all isotopes of an element add up to 1.
Since there are only two isotopes, this means:
Boron-10: f.a. = x
Boron-11: f.a. = 1 – x
Solving for x:
Boron has only two naturally occurring isotopes. The mass of boron-10 is 10.01294 amu and the mass of boron-11 is 11.00931 amu .
Use the atomic mass of boron to calculate the relative abundance of boron-11.
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