Question

The half-life of 131I is 8.04 days. (a) Convert the
half-life to seconds. (b) Calculate the decay constant
for this isotope. (c) Convert 0.500 mCi to the SI unit
the becquerel. (d) Find the number of 131I nuclei necessary
to produce a sample with an activity of 0.500 mCi.
(e) Suppose the activity of a certain 131I sample is
6.40 mCi at a given time. Find the number of half-lives
the sample goes through in 40.2 d and the activity at
the end of that period.

Here are the answers:

(a) 6.96 x 10⁵ s (b) 9.97 x 10^-7 s^-1 (c) 1.9 x 10⁴ decays/s (d) 1.9 x 10¹⁰ nuclei (e) 5, 0.200 mCi

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Answer 1