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Boron occurs as two isotopes of masses exactly 10 u and 11 u. The…
Question
Boron occurs as two isotopes of masses exactly 10 u and 11 u. The observed average atomic mass of boron is 10.81 u. Calculate the percentage abundance of the heavier isotope (mass 11 u).
✓ Verified answer: 81checked by our engine — not a guess
Step-by-step solution
Let a = % of mass-10 isotope; (100 - a) = % of mass-11 isotope.
[10a + 11(100 - a)]/100 = 10.81.
10a + 1100 - 11a = 1081 -> -a = -19 -> a = 19.
Percentage of mass-11 isotope = 100 - 19 = 81%.
Final answer81.0
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