Chemistry
posted by John .
How many halflives have passed if 87.5% of a substance has decomposed? How many if 99.999% has decomposed?
For 87.5% decomposition 1/8 is left.
(1/8) = (1/2)^3
Three half lives is the answer
Fot 99.999% decomposition, 10^5 is left.
Solve 10^5 = (1/2)^n for the number of halflives, n. Take the log of each side of the equatiuon for a quick solution.
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