SOLUTION: The half-life of a radioactive element is 131days, but your sample will not be useful to you after 70% of the radioactive nuclei originally present have disintegrated. About how ma
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-> SOLUTION: The half-life of a radioactive element is 131days, but your sample will not be useful to you after 70% of the radioactive nuclei originally present have disintegrated. About how ma
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Question 451673: The half-life of a radioactive element is 131days, but your sample will not be useful to you after 70% of the radioactive nuclei originally present have disintegrated. About how many days can you use the sample? Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! The half-life of a radioactive element is 131 days, but your sample will not be
useful to you after 70% of the radioactive nuclei originally present have disintegrated.
About how many days can you use the sample?
:
The radioactive decay equation: A = Ao*2^(-t/h), where
A = resulting amt in t time
Ao = initial amt
t = time
h = half-life of substance
:
Let Ao = 1
the
A = .3 after 131 days (70% decayed)
:
1*2^(-t/131) = .3
ln(2^(-t/131)) = ln(.3)
log equiv of exponents *ln(2) = ln(.3) = = -1.7369656
t = -1.7369656 *-131
t = +227.5 days, the substance is useful
:
;
Check on a calc: enter 2^(-227.5/131) results .300
