The atomic weight of Ga is 69.72 amu. There are only two naturally occurring isotopes of gallium: #"^69Ga# with a weight of 69.0 amu, and #"^71Ga# with a weight of 71.0 amu. What is approximate natural abundance of the #"^71Ga# isotope?

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Answer 1 · 2017-06-06T07:58:10

The natural abundance is #=36%#

Let the percentage of the isotope #""^71Ga# be #=x%#

Then,

The percentage of the isotope #""^69Ga# is #=(100-x)%#

We write the mass balance equation

#100*69.72=x*71+(100-x)*69#

#6972=71x+6900-69x#

#2x=6972-6900=72#

#x=36#

Therefore,

The percentage of the isotope #""^71Ga# is #=36%#