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Energy Change for a Nuclear Rection

 
During nuclear changes, either some mass is converted into energy or some energy is converted into mass.  Which occurs is dependent upon the specifics of the individual reaction.  From this change in mass we can calculate its energy equivalent using Einstein's equation, E = mc2.

Determining the Energy Change of a Nuclear Reaction

To find the energy change for a nuclear reaction you must know the masses of each species in the equation for the reaction.  To calculate the energy change for a nuclear reaction:

Example:  Calculate the energy change for the following nuclear reaction.  The masses of each species are given below.

1 neutron + 235--> 89Rb + 144Ce + 3 electrons + 3 neutrons

Masses:
    neutron = 1.00867 amu
    electron = 0.00055 amu
    uranium-235 = 234.9934 amu
    rubidium-89 = 88.8913 amu
    cerium-144 = 143.8817 amu

Mass of Products = 88.8913 amu + 143.8817 amu + 3 (0.00055 amu) + 3 (1.00867 amu) = 235.8007 amu
Mass of Reactants = 1.00867 amu + 234.9934 amu = 236.0021 amu
Dmass = 235.8007 amu - 236.0021 amu = - 0.2014 amu
DE = (- 0.2014 amu)(1.6606 x 10-27 kg/amu)(2.9979 x 108 m/s)2 = - 3.006 x 10-11 J
(- 3.006 x 10-11 J/atom)(1 kJ/1000 J)(6.023 x 1023 atoms/mol) = - 1.811 x 1010 kJ/mol of U-235

Note:  The negative sign indicates that this nuclear reaction is exothermic.

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