The relative atomic mass of boron (which exists in two isotopic forms {}^{10}B and {}^{11}B) is 10.81. What will be the abundance of {}^{10}B and {}^{11}B respectively (consider a sample of 100 atoms)?

  1. A. 19% and 81%
  2. B. 81% and 19%
  3. C. 38% and 62%
  4. D. 62% and 38%

Correct Answer: A. 19% and 81%

Explanation

Let the fractional abundance of {}^{10}B be x. Therefore, 10x + 11(1-x) = 10.81, which gives x = 0.19. The percentage of {}^{10}B is 19%, making {}^{11}B 81%.

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