The half-life of 131 I is 8.04 days. (a) Convert the half-life to seconds. s (b)

Question

The half-life of 131I is 8.04 days. (a) Convert the half-life to seconds.
s

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

(c) Convert 0.560 The half-life of 131I is 8.04 days. (a) Convert the half-life to seconds.
s

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

(c) Convert 0.560 (a) Convert the half-life to seconds.
s

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

(c) Convert 0.560 The half-life of 131I is 8.04 days. (a) Convert the half-life to seconds. s (b) Calculate the decay constant for this isotope. s?1 (c) Convert 0.560 ?Ci to the SI unit the becquerel. Bq (d) Find the number of 131I nuclei necessary to produce a sample with an activity of 0.560 ?Ci. 131I nuclei (e) Suppose the activity of a certain 131I sample is 6.50 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. half-lives mCi

Explanation / Answer

a)

T_1/2 = 8.04 days = ( 8.04 days ) ( 24 h ) ( 36 00 s ) = 694656 s

b)

Decya constant = 0.693 /T_1/2

= 0.693 / 694656 = 9.97*10^ -7 s^ -1

c)

0.560 * 10 ^ -6 C i = (0.560 * 10 ^ -6 ) ( 3.7* 10 ^ 10 B q ) = 20720 Bq

d)

Activity = decay constant ( N )

N =  20720 Bq /  9.97*10^ -7 s^ -1 = 2.078* 10^ 10 nucleons

e)

NUmber of half lifes is

n = 40.2 days / 8.04 days = 5 T_1/2

activity

A = ( 0.560* 10 ^ -6 Ci ) e ^ ( 0.693 ) (40.2 ) /8.04

=3.77* 10 ^ -9 Ci

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