unknown element is a mixture of isotopes ¹²⁰X and ¹²²X. The average atomic mass of X is 120.81 amu. What is the percent abundance of ¹²²X?

2 Answers

  • 1 month ago

    approximately 40 %.  Simple mass balance equation.  The presumption that isotope 120X has a mass of 120 AMU, and that 122X has a mass of 122 AMU, is, of course, likely untrue.  Only 12C has an actual mass of 12 AMU, and that is because we define AMU that way.

  • 1 month ago

    122*x + 120*(1-x) = 120.81 =>

    2x = 0.81 =>

    x = 0.405 = 40.5%

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