chemistry
posted by rick .
a sample of a radioisotope had a mass of 100.0 grams. After exactly 24 days, 6.25 grams remained. The half life of the isotope is _________

chemistry 
DrBob222
ln(No/N) = kt
No = 100
N = 6.25
t = 24 days.
Solve for k, then substitute into the equation below.
k = 0.693/t_{1/2} and solve for t_{1/2}
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