How do you find out the fractional abundance of an isotope?

December 20th, 2009 | by admin |

For instance: Chlorine has two naturally occurring isotopes, chlorine-35 (isotopic mass 34.9689 amu) and chlorine-37 (isotopic mass 36.9659 amu). If chlorine has an atomic mass of 35.4527 amu, what is the percent abundance of each isotope? How would I work this problem?

To find the percent abundance of each isotope of chlorine proceed as follows:

Let x = fraction of Cl-35
then fraction of Cl-37 must be 1-x

so

34.9689x + (36.9659)(1-x) = 35.4527

and solve for x.

I hope this helps.

  1. One Response to “How do you find out the fractional abundance of an isotope?”

  2. By Auriga on Dec 20, 2009 | Reply

    To find the percent abundance of each isotope of chlorine proceed as follows:

    Let x = fraction of Cl-35
    then fraction of Cl-37 must be 1-x

    so

    34.9689x + (36.9659)(1-x) = 35.4527

    and solve for x.

    I hope this helps.
    References :
    Personal knowledge of the author (college chemistry teacher).

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