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Worksheet: Relative Atomic Masses and Isotopic Abundance

Q1:

A sample of lithium contains a mixture of 7 L i and 8 L i isotopes, with atomic masses of 6.01512 u and 7.01600 u, respectively. The sample is 4 . 2 1 % 7 L i by mass.

Calculate to 3 significant figures the average atomic mass of the sample.

  • A 6.06 u
  • B 6.04 u
  • C 6.52 u
  • D 6.97 u
  • E 6.96 u

A second sample of lithium also contains a mixture of 7 L i and 8 L i but displays a higher abundance of 7 L i . How does the average atomic mass of this sample compare with that of the first?

  • ALower
  • BEqual
  • CHigher