A fictitious element that has two isotopes has an average atomic mass of 117.3. If 65.43% of the atoms of the element have an atomic mass of 119.8, what is the atomic mass of the other isotope?

1 Answer
Sep 6, 2017

Approx...113amu

Explanation:

The weighted average of the isotopes is equal to 117.3amu.

And thus.........with units of amu

[65.43%×119.8+34.57%×χ]=117.3

Where χmass of the other isotope....

And so we solve for χ....

χ=117.30.6543×119.80.3457=112.6amu