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Unilorin Post-UTME Chemistry 2021 (Model questions) Question 2

Question 2

Atomic Structure

An element X has isotopic masses of 6 and 7. If the relative abundance is 1 to 12.5 respectively, what is the relative atomic mass of X?

  1. A.6.0
  2. B.6.1
  3. C.6.9
  4. D.7.0
Show the answer and explanation

Answer: C (6.9)

Explanation

Relative atomic mass = (6 × 1 + 7 × 12.5)/(1 + 12.5) = 93.5/13.5 ≈ 6.9.