Latest revision as of 10:01, 9 July 2012

Amount of Radioactive Material (number of nuclei, number of moles, weigth) and the Law of Radioactive Decay

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1:

1. 3.2  • 10⁸ Bq
2. 383 Bq
3. 2.3  • 10⁹ Bq
4. 8.0  • 10⁴ Bq

2:

1. 1.77  • 10¹³ atoms.
2. 2.00  • 10¹¹ atoms.

3:

2.40 g ⁶⁰Co.

4:

1. 2.53  • 10⁵ Bq.
2. 7.21 years = 7 years and 76.7 days.

5:

The mass of ^99mTc is 20.5 ng. After one week 28 half-lives will have past, and the activity will be the following:

D = D₀  • (½)²⁸ = 4  • 10⁷ Bq  • (½)²⁸ = 0.15 Bq.

All ^99mTc has disintegrated and turned into ⁹⁹Tc. The number of ⁹⁹Tc atoms will therefore be the same as the original number of ^99mTc atoms.

[math]N=\frac{D}{\lambda} \rightarrow \frac{4\cdot 10^{7}Bq}{3.21\cdot 10^{-5}s^{-1}}=1.25\cdot 10^{12}atoms[/math]

6:

1. 1 g natural Lu contains 0.0259 g ¹⁷⁶Lu, with a half-life equal to 3.8 • 10¹⁰ years, which gives A = 51 Bq
   
2. There are two naturally occurring radioisotopes of Sm, ¹⁴⁷Sm and ¹⁴⁸Sm, which gives A = 127.24 Bq + 0.001 Bq = 127 Bq.

7:

3002 kg

8:

1. 18.5 kg
2.  After 2.455 • 10⁵ years it will be 2.299 • 10⁸ Bq ²³⁸U left, which is equal to 18.49 kg.