In a nuclear fission reaction, U-236 splits as: U-236(92) -> X-117(53) + Y-117(53) + n + n. The binding energy per nucleon of X and Y is 8.5 MeV, while that of U-236 is 7.6 MeV. If the total energy liberated equals 25N MeV, find the integer value of N.

N = 8
N = 9
N = 10
N = 7

Correct answer: N = 8

Solution

Energy released = 2*117*8.5 - 236*7.6 = 1989 - 1793.6 = 195.4 MeV. With 25N = 195.4, N ~ 7.8. The problem states 7.58 MeV for U-236 in the original, giving 2*117*8.5 - 236*7.58 = 1989 - 1788.88 = 200.12 MeV, so 25N ~ 200, N = 8.

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