SOLUTION: The radioactive element americium-241 has a half-life of 432 years. How many years will it take a 20-g mass of Americium-241 to decay to 6.8 g?

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Question 926886: The radioactive element americium-241 has a half-life of 432 years. How many years will it take a 20-g mass of Americium-241 to decay to 6.8 g?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
Q(t) = Q%5B0%5De%5E%28-kt+%29
ln(.5)/-432 = k = .0016
.......
Q(t) = Q%5B0%5De%5E%28-.0016t+%29
ln(6.8/20 )/-.0016 = t = 674.256 years