SOLUTION: The half-life of element X is 13.25 minutes, if the orginal of the sample is 2.36 kg, how long will it take in HOURS for the remaining mass to be 12.0 grams ?

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Question 1129845: The half-life of element X is 13.25 minutes, if the orginal of the sample is 2.36 kg, how long will it take in HOURS for the remaining mass to be 12.0 grams ?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The half-life of element X is 13.25 minutes,
if the original of the sample is 2.36 kg,
how long will it take in HOURS for the remaining mass to be 12.0 grams ?
:
The radio active decay formula
A = Ao*2^(-t/h) where
A = remaining amt after t time
Ao = initial amt
t = time of decay
h = half-life of substance
:
Change 2.36 kg to 2360 grams
2360*2^(-t/13.25} = 12
2^(-t/13.25) = 12%2F2360
ln%282%5E%28-t%2F13.25%29%29 = ln%2812%2F2360%29
the log equiv of exponents
-t%2F13.25ln(2) = ln%2812%2F2360%29
-t%2F13.25 = ln%2812%2F2360%29%2Fln%282%29
Using our calc
-t%2F13.25 = -7.61961
t = -13.25 * -7.61961
t = 100.9598 ~ 101 minutes
which is
101/60 = 1.68 hrs