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Homework Help: Nuclear Fisson problem

  1. Dec 1, 2008 #1
    1. The problem statement, all variables and given/known data
    A typical fission reaction is
    U(92,235) → Zr(40,98) + Te(52,135) + 2 n
    The numbers in parentheses are (Z,A) for each isotope; n stands for a neutron. The atomic masses of the isotopes are: U(92,235) = 235.043923 u; Zr(40,98) = 97.912746 u; Te(52,135) = 134.916450 u; n = 1.008665 u.
    (The atomic mass unit is 1 u = 931.5 MeV/c2 = 1.67 ×10−27 kg where c is the speed of light.)
    (a) How much mass energy is released in the fission reaction? Use this number as typical of fission reactions. (Express the answer in MeV.)

    2. Relevant equations
    None. Just seems like simple algebra to me.

    3. The attempt at a solution
    -I started by finding the mass difference between the reactant and the products, which equaled out to .197397
    -I then multiplied this number by 1.67E-27 to convert it to kilograms.
    -I then multiplied this number by the speed of light squared and obtained 2.95E-11
    -I then divided 2.95E-11 by 931.5 to get the answer in MeV, but no matter how many times I try this method I don't get the right answer! A little guidance would be appreciated if anyone has any idea! Thank you!!!
  2. jcsd
  3. Dec 1, 2008 #2
    I see your problem:

    "The atomic mass unit is 1 u = 931.5 MeV/c2"

    This equation converts mass in units of u directly to MeV. Hence you may directly multiply u with 931.5 to find the energy in MeV.
  4. Dec 1, 2008 #3
    Thank you!
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