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!

Homework Help: Energy homework problem help

  1. May 4, 2010 #1
    1. The problem statement, all variables and given/known data
    The atomic mass of gold-197 is 196.96654 u.

    How much energy is required to completely separate the nucleons in a gold-197 nucleus?

    2. Relevant equations

    E = 196.96654 u x 931.5

    3. The attempt at a solution
    I did the above calculation and got 1.83e5 MeV but im pretty sure I did this completely wrong. help?
     
  2. jcsd
  3. May 5, 2010 #2

    kuruman

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Re: Energy

    Does gold-197 have 196.96654 nucleons? How many does it really have?
     
  4. May 5, 2010 #3
    Re: Energy

    To separate the nucleons completely, you must supply the binding energy of the nucleus:

    Eb = [m(nucleons) - m(nucleus)]c^2 (Note that mass is in kg).

    Alternatively, use 931.5MeV / u to simplify the calculation (and use only atomic mass units):

    Eb = [m(nucleons) - m(nucleus)] x 931.5 MeV/u

    If the binding energy is Eb, what is the binding energy per nucleon?


    Also, remember that the atomic mass includes electrons, so you will have to subtract the mass of these in order to obtain the mass of the nucleus only.

    BTW, I think you did the calculation to find the mass-energy of the gold atom, rather than the energy required to separate its nucleons.
     
    Last edited: May 5, 2010
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook