Homework #1 Problem Set
DECAY KINETICS, EQUILIBRIUM, DATING
tor
the less
1. If 140Ba is freshly separated from a fission product mixture and found to contain 125
milliCi, (a) what is the activity of 14°La that will grow into the sample in 17.2 hr? (b)
What is the maximum activity of 140La that will ever be present in the sample, and (c)
when will it occur?
a. A=
Ti
T₂-T2
x Ap * (e-Azt – e-dzt)
A=
12.75 d
12.75 d -1.678
x 125 mCi x (e 306 h*17.2 h
In2
In2
e 40.272 h
x
17.2 ") = 31.38 mCi
b. A=
12.75 d
12.75 d-1.678
Inz
x 125 mCix (e 12.75 d*
x 5.65 d
In2
e 1.679 d
a *5.65 d) = 91.3 mci
c. tm = 1.4427 x
12.75 x 1.678 12.75
X In
12.75-1.678 1.678
= 5.65 days
the wa
2
A short-lived radioisotone