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Binding Energy Concepts

  1. Aug 11, 2007 #1
    1. The problem statement, all variables and given/known data
    Consider the fission reaction in which 236U92 breaks up into 141Ba56 and 3 neutrons and an unknown fragment. Which of the following statements are true about this fission reaction in particular and nuclear reaction energies in general? You are given a plot of the binding energy (BE) per nucleon to help you.
    [​IMG]

    True False the unknown fission fragment will have Z = 33
    True False the unknown fission fragment will have A = 95
    True False a heavy nucleus (like uranium) can become more stable via a reaction that moves it back to the left on the BE curve
    True False a heavy nucleus (like uranium) releases less energy in a single fission reaction than in one alpha decay
    True False the fission products (two fragments plus 3 neutrons) have less total mass than the original 236U

    3. The attempt at a solution

    1. Z= Atomic Mass so true; must be equal before and after the equation
    2. A= Atomic # so true; must be equal before and after the equation
    3. Not sure, i thikn its false because of the graph, not sure about this one
    4. Also not sure about this, but believe false, because it has alpha decay.
    5. The total mass must be equal before and after the reaction

    My answers are in bold, and above are my reasons, i cant figure out what im doing wrong. Can anyone help?

    Thanks
     
  2. jcsd
  3. Aug 12, 2007 #2
    bump, any1 know?
     
  4. Aug 12, 2007 #3

    learningphysics

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    I think you have one and two right. I think 3 is True because higher binding energy -> more stability...

    Not sure about 4.

    But 5 is true... right side has lower mass because energy has been released...
     
  5. Aug 12, 2007 #4
    Turns out 1 and 2 are false?? Any1 have any clue why? that makes no sense
     
  6. Aug 12, 2007 #5

    learningphysics

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    Oops... sorry A = 92... 236-141-3... and Z = 36 (92-56)

    A is the total number of protons+neutrons.
    Z is the total number of protons.

    I was mixing up number of protons and neutrons...

    So yes, they're false.
     
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