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Homework Help: Disintegration Energy of Beta Plus Decay

  1. Jan 16, 2016 #1
    1. The problem statement, all variables and given/known data
    The radionuclide 11C decays according to
    116C → 115B + e+ + v
    Show that the disintegration energy is given by
    Q = (mC - mB - 2me) c2

    2. Relevant equations
    Q = (mi - mf) c2

    3. The attempt at a solution

    Q= (mC - mB - me) c2

    Im probably missing something obvious but I can't see where the 2me comes from.
     
  2. jcsd
  3. Jan 16, 2016 #2

    TSny

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    The key is to remember that the given masses mC and mB are atomic masses, not nuclear masses.
     
  4. Jan 16, 2016 #3
    But that leads me to
    Q = ((mC+6mE) - (mB + 5mE + mE))c2

    Which gives me
    Q= (mC + mB)c2
     
  5. Jan 16, 2016 #4

    TSny

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    To get the nuclear mass of the carbon, should you add 6 electrons to the atomic mass?
     
  6. Jan 16, 2016 #5
    Ah i think I understand

    Q = ((mC- 6mE) - (mB - 5mE + mE))c2

    Q = (mC - mB - 2me) c2

    Is this right?
     
  7. Jan 16, 2016 #6

    TSny

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    Looks right. Good.
     
  8. Jan 16, 2016 #7
    Thank You :)
     
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