Problem set 3

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

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Calculate the rate of disintegration of the following:

  1. 1.0 • 1013 atoms 99mTc.
  2. 1.0 • 1014 atoms 14C.
  3. 1.0 grams 239Pu.
  4. 1.0 gram 235U.


Calculate the amount of atoms in the following nuclides:

  1. 10 MBq of 32P
  2. 200 kBq of 131I


A source of 60Co has a rate of disintegration equal to 1.0 • 1014 Bq. What is the mass of 60Co in grams?


A preparation labelled 3H disintegrates with 3.0 • 105 Bq.

  1. What is the rate of disintegration after 3 years?
  2. How long does it take for the rate of disintegration to reach 2.0 • 105 Bq?


A patient is administered 4.0 • 107 Bq 99mTc in connection with a nuclear medicine examination. Calculate the amount of mass of 99mTc injected in the patient. The daughter nuclide 99Tc is radioactive, but has a very long half-life. Show that the total rate of disintegration in the patient is insignificant one week after the examination.


Calculate the rate of disintegration of the following:

  1. 1.0 g natural Lu-metal
  2. 1.0 g natural Sm-metal


Recently it was showed that natural Bi is radioactive. How much amount of Bi is required to give a disintegration rate of 10 Bq?


In nature 234U exist in equilibrium with 238U as a daughter product.

  1. How much 238U has an equivalent disintegration rate as 1g 234U?
  2. Given the amounts from a) is separated as pure 238U and 234U, how many percent has the amount of 238U decreased when the amount of 234U is halved?