U-235 fission => intermediate weight nuclei with higher (stronger) binding energies.
The general equation for fission of U- 235 is
U-235 + neutron => U-236 => Ba-144 + Kr-89 + 3 neutrons + Binding Energy (Other intermediate weight nuclei are also formed, but this is just for this illustration.)
Binding Energy is the energy released on formation of specified nuclei. Binding Energy is typically measured in electron volts (eV) where MeV is Megaelectronvolts ( = 1.6022E-16 Kilojoules) .
The binding energy of U-235 = 7.56 MeV/nucleon
The binding energy of Ba-144= 8.26 MeV/nucleon
(BE U-235) - (BE Ba-144) = 7.56 - 8.26 MeV/nucleon = - 0.70 MeV/nucleon
Converting to Kj/nucleon:
=> - 0.70 MeV/nucleon ( 1.6022E-16 Kj/MeV ) = - 1.1215E-16 Kj/nucleon
Converting to Kj/mole:
=> - 1.1215E-16 Kj/nucleon (6.023E+23 nucleons/mole) = - 6.8E+07 Kj/mole
NOTE: The Heat of Combustion of candle wax is ~ 1.3E+04 Kj/mole*. Nuclear fission gives ~ 5000 times more energy per mole.
- Since candle wax is a mixture of hydrocarbons, the Heat of Combustion is only an approximation but suffices as a general comparison for this illustration. (http://tdwhs.nwasco.k12.or.us/staff/bfroemming/Heatcandle.html)
The fission products have less mass than the reactants, and this mass defect is converted into energy.
A typical equation for nuclear fission is
Calculate the mass of the reactants
Calculate the mass of the products
Calculate the mass defect
Convert the mass defect to energy
This is the energy released by the fission of one atom of uranium-235.
The energy released by one gram of uranium-235 is
In contrast, the energy released by burning 1 g of paraffin wax is 42.0 kJ/g.
The fission of 1 g of uranium-235 releases nearly two million times the energy as the combustion of 1 g of paraffin wax.