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(Amount of radioactive material (number of nuclei <-> number of moles <-> weigth) and law of radioactive decay)
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= Amount of radioactive material (number of nuclei &lt;-&gt; number of moles &lt;-&gt; weigth) and law of radioactive decay <br>  =
 
= Amount of radioactive material (number of nuclei &lt;-&gt; number of moles &lt;-&gt; weigth) and law of radioactive decay <br>  =
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====== Written and developed by [http://www.mn.uio.no/kjemi/english/people/aca/phoff/index.html Prof. Per Hoff]&nbsp;(uio)&nbsp;  ======
  
 
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Revision as of 10:51, 22 June 2012

Amount of radioactive material (number of nuclei <-> number of moles <-> weigth) and law of radioactive decay

Written and developed by Prof. Per Hoff (uio) 


1:

  1. 3.2  • 108 Bq
  2. 383 Bq
  3. 2.3  • 109 Bq
  4. 8  • 104 Bq


2:

  1. 1.78  • 1013 atoms.
  2. 2  • 1011 atoms.


3: 2.40 g 60Co.


4:

  1. 2.53  • 105 Bq.
  2. 7.19 years = 7 years and 68 days.


5: The mass of 99mTc is 20.5 ng. After one week 28 half-times 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 therfore 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 år. This gives D = 51 Bq
  2. There are two naturally occuring radioisotopes of Sm, 147Sm and 148Sm, which gives D = 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.