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Homework Help: Fusion reaction

  1. Sep 24, 2010 #1
    1. The problem statement, all variables and given/known data

    A nuclear reaction being studied for its potential as a source of fusion power is:

    21H + 31H -> 42He + 10n

    1) calculate energy in MeV released when two atoms fuse according to the reaction above.
    2) calculate the energy in joules released per mole of reactants. (ie. one mole of H-2 and one mole of H-3)

    3. The attempt at a solution

    1) the answer is 17.59 Mev
    and i dunno how to go about 2)

    i know combined they release that energy found in part 1)... but im not sure how to divide that energy up between them. is it done on a ratio of 2:3 by atomic mass? or is it done by mass in kg? i just dont know the connection there...
     
  2. jcsd
  3. Sep 25, 2010 #2

    rock.freak667

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    Well if you know the masses of 21H and 31H, since they are both currently 1 mole, you can just add the atomic masses, which would be in the units kg/mol.

    E=mc2
     
    Last edited: Sep 25, 2010
  4. Sep 25, 2010 #3
    the mass of 21H is 2.014102 so E is just 2.014102c^2?
    same for 31H.
     
  5. Sep 25, 2010 #4

    rock.freak667

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    It is 2.014102u where u = 1.66053886 × 10-27 kg.
     
  6. Sep 25, 2010 #5
    yeah, i used that conversion, just didnt clarify.

    E of 21H = 3.01*10^-10J
    E of 31H = 4.507*10^-10J
     
  7. Sep 25, 2010 #6

    rock.freak667

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    Sorry, I thought your question was asking something else. Just convert the value you got to Joules, then you only have 2 moles of reactants so, that the energy per unit mole of reaction is just Ereactant/2.
     
  8. Sep 25, 2010 #7
    ohh... so the atomic masses and whatnot of the elements isnt even relevant? the energy is just half anf half?
     
  9. Sep 25, 2010 #8

    rock.freak667

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    Well you are finding per mole of reactant and not something like per mole of H-2 which I think would work out to be different, but my reasoning of the problem could be wrong.
     
  10. Sep 25, 2010 #9
    2) calculate the energy in joules released per mole of reactants. (ie. one mole of H-2 and one mole of H-3)


    so its energy per H-3 and per H-2.
     
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