Question 110865: Half life question. Please help if possible.
The half-life of the radioactive element plutonium-239 is 25,000 years. If 16 grams of plutonium-239 are initially present, how many grams are present after 25,000 years? 50,000 years? 75,000 years? 100,000 years? 125,000 years?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! :
The half-life of the radioactive element plutonium-239 is 25,000 years. If 16 grams of plutonium-239 are initially present, how many grams are present after 25,000 years?
:
The half life formula: A = Ao(2^(-t/h) where
Ao = original amt
t = time
h = half life of the material
A = resulting amt
:
Substituting for plutonium-239:
:
A = 16(2^(-25000/25000)
A = 16(2^-1); (you know that 2^-1 = 1/2 or .5, try it on a good calc)
A = 16 * .5
A = 8 oz, as you would expect
:
:
50,000 years?
:
A = 16(2^(-50000/25000)
A = 16(2^-2); (2^-2) = 1/4)
A = 16 * .25
A = 4 oz after 50k yrs
:
:
75,000 years?
:
A = 16(2^(-75000/25000)
A = 16(2^-3)
A = 16 * .125
A = 2 oz after 75k yrs
:
you should be able to do the rest of them now
100,000 years? 125,000 years?
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