Naturally occuring boron is 80.20% boron-11 (atomic mass= 11.01 amu) and 19.80% of some other isotopic form of boron. What must the atomic mass of this second isotope be in order to account for the 10.81 amu average atomic mass of boron? (Write the answer to two decimal places)

Question

jfraser · Answer

The average atomic mass is made up of the two isotopes, and you know the percentages of each. Set up an algebraic equation for finding a weighted average, and solve for the mass of the second isotope