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Homework Help: Nuclear reactions

  1. Mar 13, 2008 #1
    calculate the amount of energy released in the fission of a U-235 nucleus.
    http://www.dummies.com/WileyCDA/DummiesArticle/Nuclear-Fission-Basics.id-1669.html
    Given:
    Masses of the particles:
    U-235 = 234.9993u
    n=1.008
    Ba=140.883u
    Kr=91.905u

    what i did was i used delta E=mc^2, where m is the mass of n...which is 1.008.. and i get 1.5x10^-10... why is this wrong?/
     
    Last edited by a moderator: Apr 23, 2017
  2. jcsd
  3. Mar 13, 2008 #2

    mgb_phys

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    The energy given off is the mass difference between the original U and the total of the decay products.

    U235 = 234.9993
    Ba+Kr+n=140.883+91.905+1.008 = 233.796
    difference = 1.203 then just E=mc^2
     
  4. Mar 13, 2008 #3
    thanks:)
     
  5. Mar 13, 2008 #4
    delta E=1.795x10^-10J....is this answer correct?
     
  6. Mar 13, 2008 #5
    i got it:)...the answer is 2.82x10^-11J.
     
  7. Mar 13, 2008 #6

    mgb_phys

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    If you did the arithmetic correctly!
    Typical U235 fission is around 200Mev or 3E-11J but depends on the exact breakup products
    with U235->Ba + Kr you would normally get 2 'extra' neutrons so your free energy is only about 0.2u
     
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