The half-life of 222 Rn is 3.83 days. (a) Convert the half-life to seconds. 1 s
ID: 1677170 • Letter: T
Question
The half-life of 222Rn is 3.83 days. (a) Convert the half-life to seconds.1 s
(b) Calculate the decay constant for this isotope.
2 s-1
(c) Convert 0.54 µCi to the SI unitthe becquerel.
3
Your response is off by a multiple often. Bq
(d) Find the number of 222Rn nuclei necessaryto produce a sample with an activity of 0.54 µCi.
4
Your response is off by a multiple often. 222Rn nuclei
(e) Suppose the activity of a certain 222Rn sample is6.20 mCi at a given time. Find the numberof half-lives the sample goes through in 40.2 d and the activity atthe end of that period.
5 half-lives
6
Your response differs from the correct answerby orders of magnitude. mCi
(a) Convert the half-life to seconds.
1 s
(b) Calculate the decay constant for this isotope.
2 s-1
(c) Convert 0.54 µCi to the SI unitthe becquerel.
3
Your response is off by a multiple often. Bq
(d) Find the number of 222Rn nuclei necessaryto produce a sample with an activity of 0.54 µCi.
4
Your response is off by a multiple often. 222Rn nuclei
(e) Suppose the activity of a certain 222Rn sample is6.20 mCi at a given time. Find the numberof half-lives the sample goes through in 40.2 d and the activity atthe end of that period.
5 half-lives
6
Your response differs from the correct answerby orders of magnitude. mCi
Explanation / Answer
(a)
the decay constant is given by
= ln 2 / T1/2
= ln 2 / (3.83 d) (8.64 x104 s / d)
= ....... s-1
(b)
we know that
R = N
so the required number of nuclei will be
N = R /
= ........ nuclei
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