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Homework Help: Bombardment of Nitrogen-14 with an alpha particle

  1. Jun 17, 2017 #1
    When alpha particles, having kinetic energy 3.0000 MeV bombard nitrogen-14 nuclei, oxygen-17 forms and the reaction releases a proton. Calculate the kinetic energy shared by the reaction products.
    Nitrogen-14 = 14.000307 amu
    Helium-4 = 4.00260 amu
    Oxygen-17 = 16.99913 amu
    Proton = 1.00727 amu
    1 amu = 931 MeV

    Attempt at question:
    I cannot derive the textbook answer (1.65 MeV). I found the increase in mass to be 0.00073 amu which equals 0.67963 MeV. I subtract this from 3.0000 MeV, but I got instead 2.32037 MeV. Does anyone know how to obtain the textbook solution? Thanks a lot.
  2. jcsd
  3. Jun 17, 2017 #2
    If you want to calculate the q-value of the reaction you must have a better precision in your atomic mass (see https://www-nds.iaea.org/amdc/ame2016/mass16.txt)
    If you take this mass number you will have Q=-1.192 MeV. Q <0 because the reaction is endothermic (threshold reaction)
  4. Jun 17, 2017 #3


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    2017 Award

    Staff: Mentor

    You should use the isotopic mass of 1H, otherwise you miss an electron (the other isotope masses are with electrons).

    If I calculate it, the reaction is not even possible.

    Edit: You have a typo in the nitrogen mass, there is one more zero than it should be.

    I get 1.81 MeV.
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