Question

the atomic mass of the 2 stable isotopes of boron are 10 & 11. calculate atomic mass of boron?
HELP.

Answer 1

Explanation:

ANSWER

Let B-10 = x%

and B-11 = (100-x)%

average atomic mass = 10x + (100 - x)/100 = 10.80

10x + 11(100 - x) = 1080

10x + 1100 - 11x = 1080

x = 20

B-10 = 20% and B-11 = (100-20) = 80%

Thus, the percentage of a heavier isotope is 80%.

Hence, the correct option is A

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