1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Nuclear Fission of 1g of Uranium 235

  1. Nov 7, 2011 #1
    1. The problem statement, all variables and given/known data

    What is the amount of energy released when 1g of uranium 235 undergoes fission? Fission of uranium is: uranium + n -> Ba + Kr +12n.

    2. Relevant equations

    E=Δmc^2

    3. The attempt at a solution

    I found the mass of the reactants to be 236.05256u and the products to be 235.92392u.
    Thus Δm=-0.12864u

    There are 2.56207x10^21 nuclei in 1g.

    Therefore the energy needed is -165.122 J/g using E=Δmc^2. Is this the correct answer?
     
  2. jcsd
  3. Nov 8, 2011 #2
    You need to convert the Δm into kg using the information that 1u = 1.66 x 10^-27kg
    Then use E = mc^2 with this mass in kg (c = speed of light 3 x 10^8m/s)
    This is the energy released by each fission of U235.
    Multiply by the number of nuclei undergoing fission.
     
  4. Nov 8, 2011 #3
    Sorry clicked submit. Look below
     
    Last edited: Nov 8, 2011
  5. Nov 8, 2011 #4
    I did convert u to kg. I got -165.122 J/g, which I think is really low for Uranium. Can you check my answer? Is my change in mass right?
     
  6. Nov 8, 2011 #5
    Your Δm =0.12864u when converted to kg becomes 0.12864 x 1.66 x 10^-27 kg
    =2.14 x 10^-28kg. This is the mass to use in E = mc^2
    This is the energy released in 1 fission.
    For 1g of material multiply by the number of atoms in 1g (I agree with the number you got)
    When I did the calculation I got 49.2J
     
    Last edited: Nov 8, 2011
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook