Question

Antimony, Sb, has two stable isotopes: 121Sb, 120.904u, and 123Sb, 122.904u. What is the percent abundance of 121Sb? (Tip: fractional abundances of isotopes must equal 1)

[1] 121.76

[2] 0.5720

[3] 57.20

[4] 0.4280

[5] I need more information to be able to answer this question

Answer 1

ANSWER:

Option (5) is the correct answer. We need more information to solve the question. If the percentage abundance of 123 Sb is given then the percentage abundance of 121 Sb can be calculated. Because the sum of the percentage of abundance is equal to 100. Similarly the percentage abundance of 121 Sb can be calculated if the fractional abundance of 123 Sb or 121 Sb is given. For example if the fractional abundance of 121 Sb is 0.5720 then the percent abundance is given as 0.5720 X 100 = 57.20 %

Similarly if fractional abundance of 123 Sb is given that of 121 Sb can be calculated. For example if the fractional abundance of 123 Sb is 0.4280. The fractional abundance of 121Sb is 1.000 - 0.4280 = 0.5720

Then the percentage abundance of 121Sb is given as = Fractional abundance X 100 = 0.5720 X 100 = 57.20 %