Use whatever data you need from the ALEKS Periodic Table to determine the identity, mass and natural abundance of the other isotope, and complete the table.

Question

There are only two naturally-occuring stable isotopes of boron. The mass and natural abundance of one of them is listed in the table below. Use whatever data you need from the ALEKS Periodic Table to determine the identity, mass and natural abundance of the other isotope, and complete the table.

Be sure your answers have the correct number of significant digits.

isotope= ^10B, mass amu = 10,013, natural abundance 19.9%

isotope= __B, mass amu = ___, natural abundance ___%

Can someone explain this to me

Answer 1

I don't know what the ALEKS periodic table is, nor do I have one, so I'll assume they want you to use the atomic mass of boron that is in your particular table. In mine, it is listed as 10.81 amu. Now, this is a weighted average of the known isotopes. We are told that one isotope is 10.013 amu and it has an abundance of 19.9%. We are asked to find the abundance and mass of the remaining isotope.

Since there are only 2 isotopes, the % abundance is simply 100% - 19.9% = 80.1%

Now, we can find the mass of this second isotope using the following formula/equation:

% x mass + % x mass = average mass

(0.199 x 10.013) + (0.801 x B) = 10.81

1.99259 + 0.801B = 10.81

B = 11.02 amu = mass of the other isotope