Problem: The average atomic masses of some elements may vary, depending upon the sources of their ores. Naturally occurring boron consists of two isotopes with accurately known masses (10B, 10.0129 amu and 11B, 11.0931 amu). The actual atomic mass of boron can vary from 10.807 to 10.819, depending on whether the mineral source is from Turkey or the United States. Calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.

FREE Expert Solution

We are being asked to calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.


We can use the following equation:


Atomic Mass=[mass×f.a.]isotope 1+[mass×f.a.]isotope 2


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.


Part A. Calculate the percent abundance leading to the actual atomic mass of boron equal to 10.807 amu


We’re given the following values:

Average Atomic Mass = 10.807 amu

10B: Mass = 10.0129 amu           f.a. = x

11B: Mass = 11.0931 amu           f.a. =1-x


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Problem Details

The average atomic masses of some elements may vary, depending upon the sources of their ores. Naturally occurring boron consists of two isotopes with accurately known masses (10B, 10.0129 amu and 11B, 11.0931 amu). The actual atomic mass of boron can vary from 10.807 to 10.819, depending on whether the mineral source is from Turkey or the United States. Calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.

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