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For the following fusion reaction, Calculate change in energy per mole.( Answer in J/mole)
2H1 + 2H1 ---> 3H1 + 1H1
(the mass number is in front of the atom and the atomic number is behind the atom)

Given info:Atoms with their masses(amu)
H-1 1.00782
H-2 2.01410
H-3 3.01605
He-3 3.01603
He-4 4.00260
neutron 1.00866

I know delta E=(C^2)(delta m)
and I know delta m= products mass- reactants mass
and I know 1 amu = 1.661X10^-27 Kg

I got delta E= -0.297 x 10^-6 but still my answer is wrong.

  • chemistry - ,

    You didn't show all of your work and I've not been able to obtain your same numbers. One possible problem may be the amu conversion.
    I think mass = 4.02387 on the right and 4.02820 on the left. delta m = 4.33E-3 amu/atom which = 4.33E-3 g/mol and we convert that to kg (4.33E-6) and multiply by c^2 (3E8 m/s squared). You may want to use a more precise value for c. See if that won't give you the ok.

  • chemistry - ,

    I'm getting 8.355E-22 Kg on for reactants, and 8.322E-22 Kg for products.

    I multiplied each mass they gave us in amu by 1.661E-27 to get it in Kg.

  • chemistry - ,

    You can do that (it's a lot of extra work) but when you finish you have kg/atom and you must multiply all of that by 6.02E23 to obtain kg/mol. However, I still don't obtain your numbers. When done your way you open yourself up to a lot of rounding errors.
    Try what I outlined above and see if it isn't simpler. In fact, I never use the 1.661E-27 factor BECAUSE it cancels out if we want J/mol.
    amu/atom x (1g/6.022E23 amu) x (6.022E23 atom/mol) = grams/mol. Note that 1g/6.022E23 (the second term) = 1.661E-24 g/amu which is where the 1.661E-27 kg/amu comes from.

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