Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Q Value for spontaneous fission and neutron induced fission

  1. Aug 31, 2011 #1
    1. The problem statement, all variables and given/known data
    What is the Q value in units of MeV in each of the following processes?

    i) The spontaneous fission of 232U92 to 145La57 and 87Br35

    ii) The neutron induced fission of 232U92 to 146La57 and 87Br35

    Explain why heavy nuclei such as 232U92 do not usually undergo fission.

    [Masses given in atomic mass units are 232U92 232.0372; 145La57 144.9217; 146La57 145.9255; 87Br35 86.9203; n 1.0087]


    There are loads of equations for different Q values depending on the type of decay it undergoes. I'm not sure which to use.

    Also, I think I need to convert the atomic mass units into something else but I'm not entirely sure what?

    I basically don't know where to start with it!
  2. jcsd
  3. Sep 2, 2011 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Use what is given to you. You call these decays, but are they really that? What is a better name for the process in which a uranium nuclide becomes a lanthanum and a bromine nuclide?
    Why convert? Use what is given to you.
    Start by writing an equation for a given process, then make sure it conserves energy.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook