Michelle is trying to find the average atomic mass of a sample of an unknown
element. She finds that her sample contains 59.34% of an isotope with a mass of
113.6459, while the rest of the sample is an isotope with a mass of 115.8488. What
is the average atomic mass of her sample? Please round your answer to 0.01 amu.

Respuesta :

The average atomic mass of her sample is 114.54 amu

Let the 1st isotope be A

Let the 2nd isotope be B

From the question given above, the following data were obtained:

  • Abundance of isotope A (A%) = 59.34%
  • Mass of isotope A = 113.6459 amu
  • Mass of isotope B = 115.8488 amu
  • Abundance of isotope B (B%) = 100 – 59.34 = 40.66%
  • Average atomic mass =?

The average atomic mass of the sample can be obtained as follow:

[tex]Average \: atomic \: mass \: = \frac{mass \: of \: A \times A\%}{100} + \frac{mass \: of \: B \times B\%}{100} \\ \\ Average \: atomic \: mass \: = \frac{113.6459\times 59.34}{100} + \frac{115.8488\times 40.66}{100} \\ \\ Average \: atomic \: mass \: = 114.54 \: amu \\ \\ [/tex]

Thus, the average atomic mass of the sample is 114.54 amu

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