Given: The average energy released per fission of P 94 239 u is 180 MeV and the amount of P 94 239 u is 1 kg.
239 gof P 94 239 u contains 6.023× 10 23 atoms.
Let N be the number of atoms present in 1 kgof P 94 239 u.
The number of atoms contain by 1 kg of P 94 239 u is given by,
N= 6.023× 10 23 239 ×1000 =2.52× 10 24 atoms
Let E t be the total energy released in the fission.
E t =E×N
Where, the average energy released per fission of P 94 239 uis E.
By substituting the given values in above equation, we get.
E t =180×2.52× 10 24 =4.536× 10 26 MeV
Thus, the energy released by the fission of 1 kgof P 94 239 uis 4.536× 10 26 MeV.