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The half-life of 222 Rn is 3.83 days. (a) Convert the half-life to seconds. 1 s

ID: 1758691 • 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 0.53 µCi to the SI unitthe becquerel.
3 Bq

(d) Find the number of 222Rn nuclei necessaryto produce a sample with an activity of 0.53 µCi.
4222Rn nuclei

(e) Suppose the activity of a certain 222Rn sample is6.30 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 mCi (a) Convert the half-life to seconds.
1 s

(b) Calculate the decay constant for this isotope.
2 s-1

(c) Convert 0.53 µCi to the SI unitthe becquerel.
3 Bq

(d) Find the number of 222Rn nuclei necessaryto produce a sample with an activity of 0.53 µCi.
4222Rn nuclei

(e) Suppose the activity of a certain 222Rn sample is6.30 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 mCi

Explanation / Answer

a)
         Half life: 3.83 days             3.83 days * 24 hours * 60 min * 60 s  = 330912   s b)   decay constant   = 0.693 / T1/2                                    =  0.693 / 330912 s                                       = 2.0942 x10-6   s-1 c)   Given :         0.53 Ci  =    0.53 x 10-6 Ci                          =   0.53 * x 10-6   * 3.7 x 1010 Bq                             =     19,610 Bq d)           Weknow that

          Numberof nuclei = Activity  / decayconstant                                               = 19610  / 2.0942 x10-6                                      = 9.363 x109   222Rn nuclei
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