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: Binding Energy for Hydrogen

  1. Sep 8, 2009 #1
    1. The problem statement, all variables and given/known data
    Find the binding energy for hydrogen in kJ/mol through positron emission.

    4(11H) → 42He + 2(0+1ß)

    2. Relevant equations
    Mass of Hydrogen: 1.0079 amu
    Mass of Helium: 4.0026 amu
    1 amu = 1.6605 x 10-27kg

    3. The attempt at a solution
    Here is what I did:

    Eb= ((number of protons)xmass hydrogen)-mass of helium)*1.6605x10-27kg/amu)*c^2
    Eb = ((4*1.0079 - 4.0026) * 1.6605*10-27)*(2.998x108)2
    Eb= 4.33x10-12 kg m2/s2 = 4.33x10-12 J
    Eb = 4.33 x 10-15 kJ
    Eb = 4.33 x 10-15 * 6.022 x1023
    Eb = 2.61 x 109 kJ/mol
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 9, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Haven't you neglected the mass of the 2 positrons?

    In the equation, E=Δmc2, the Δm = mass of reactants - mass of all products (including positrons)
  4. Sep 9, 2009 #3
    Isn't a positron basically massless considering it would just have the mass of an electron or will it make a big difference?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook