SOLUTION: Sodium – 24 has a half life of 15 hours. How many grams of a 900 G sample will remain after 90 hours?

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Question 1102741: Sodium – 24 has a half life of 15 hours. How many grams of a 900 G sample will remain after 90 hours?
Found 2 solutions by ikleyn, Boreal:
Answer by ikleyn(52903) About Me  (Show Source):
You can put this solution on YOUR website!
.
90 hours = 15*6 = 6 times half-life  ===================>


The amount of the Sodium-24 remained after 90 hours will be  900%2F2%5E6 = 14.0625 grams.


Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
FV=PV(1-d)^n, n is number of periods, d the rate of decay, PV start, and FV end
FV=0.5 PV after 1 period
therefore, 0.5=(1-d)
d=0.5
FV=900(0.5)^n
90 is 6*15, so n=6
FV=900(0.5^6)=14.06 gm