# chemistry

Gallium is a metal with a wide variety of uses. Some of its applications include computer memory chips, light emitting diodes and lasers. Radioactive isotopes of gallium are used to image the human body and locate tumors. Naturally occurring gallium consists of two isotopes. One of those isotopes is 71Ga with an isotopic mass of 70.9247050 amu and an abundance of 39.892%. What is the mass number of the other isotope?

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1. 71 mass number has abundance of 39.892
let x = mass number of other isotope. % abundance is 100-39.892 = 60.108
Then 71(0.39892) + 0.60108x = 69.723 (from periodic table)
28.32 + 0.60108x = 69.723
x = (69.723-28.32)/0.60108 = 68.9 which I would round to 69 as the probable whole number for the mass number.

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2. 68.88

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3. the answer should be rounded to the closest whole integer, which should be 69.
The equation can be seen as:
(70.9247050)(.39892)+(W)(1-x)=Gallium atomic mass

1-x= 1-(other isotope abun.)
1- .39892= .60108
so plug that in and solve for W, the mass number of the unknown isotope.

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