The half-life of Tungsten-181 is 121 days. If you start with 3 pounds of it, how much do you have after 7 years?

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Answer 1 · 2018-05-07T06:08:04

#approx 1.32 times 10^-6# pounds

Convert the number of years into days so that we can determine how many half-lives have passed.

7 years= #(365.25 times 7)=2556.75# days

#2556.75/(121) approx 21.13# Half-lives

Use the equation:

#M=M_0 times (1/2)^(n)#

#n#= number of half-lives

#M_0#= initial mass

#M#=final mass

Hence, as the initial mass is 3 pounds and the number of half-lives is 21.13:

#M=3 times (1/2)^(21.13)#

#M approx 1.32 times 10^-6# pounds remain after 7 years.