SOLUTION: The half-life of 234U, uranium-234x10to the 5th power year. If 98.1% of the uranium in the original sample is present, what length of time(to the nearest thousand years has elapsed

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Question 566146: The half-life of 234U, uranium-234x10to the 5th power year. If 98.1% of the uranium in the original sample is present, what length of time(to the nearest thousand years has elapsed?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The half-life of 234U, uranium-234x10to the 5th power year.
If 98.1% of the uranium in the original sample is present, what length of time(to the nearest thousand years has elapsed?
:
The radioactive decay formula: A = Ao*2^(-t/h)
where:
A = resulting amt after t yrs
Ao = initial amt
h = half-life of substance
t = time
:
Using the half-life value of 2.44(10^5) yrs, initial amt as 1
1*2^(-t/2.44(10^5)) = .981
using nat logs
-t%2F%282.44%2810%5E5%29%29*.693 = -.0192
:
-t%2F%282.44%2810%5E5%29%29 = %28-.0192%29%2F.693
t = -2.44(10^5) * -.027675
:
t = +6753 ~ 7,000 yrs