Question

At 9:30 am, an MAA kit was reconstituted using 125 mCi in a final volume of 5.5 ml. The kit contained 3,600,000 particles. Approximately, how many particles would be in a 4 mCi dosage at 1 pm?

1.15 x 10^5

1.73 x 10^5

7.69 x 10^4

3.14 x 10^4

2-The decay rate (in dpm) for a 4 mCi source of ²⁰¹Tl is

5.6 x 10¹³

8.9 x 10⁹

1.5 x 10⁸

148

3-A radionuclide decays from 8 nCi to 4 pCi in 5 minutes. The half-life of this radionuclide (in minutes) is:

2.2

0.55

0.46

2.5

5

Answer 1

1. The activity is proportional to the number of particles. Therefore the number of particle is given by

Answer: Option 1

2. The decay rate of 1 Ci is 3.7*10¹⁰ Bq. which means disintegrations per second. Therefore 4 mCi is

Answer: Option 3

Just as the number of molecules decreases to half in 1 half life so does the activity. Therefore in this case the number of half lives that have passed in 5 minutes is given by

Therefore 1 half life is

Answer: Option 3