Uranium-235 may undergo fission via the following reaction: 235U92 ----> 141Ba56

Question

Uranium-235 may undergo fission via the following reaction:
235U92 ----> 141Ba56 + X + 2n
SHORT QUESTIONS.
A. Identify the fission fragment X. Write down its element symbol with appropriate sub- and super-script in
the answer box. You may refer to the periodic table.
B. The energy released in the above nuclear reaction is 173.2 MeV. Calculate the mass of the nucleus of the
fission fragment X. Give your answer in atomic mass units (u). Keep four significant figures in your answer.

Additional data. You may not need all of it.
1 eV = 1.602 x 10^-19 J
1 MeV = 106 eV
1 u (atomic mass unit) = 1.6605 x 10^-27 kg
Mass - energy equivalence: 1 u = 931.494 MeV
mp= mass of proton = 1.007825 u
mn = mass of neutron = 1.008665 u
me = mass of electron = 5.4858 x 10-4
u
c = speed of light = 2.998 x 10^8 m s-1
? = Stefan-Boltzmann constant = 5.672 x 10^-8 J s-1 m-2 K-4
? = Earth's average planetary albedo = 0.34
rE = radius of planet Earth = 6370 km
Solar constant for Earth: S ? 1370 Wm-2
Nuclear masses :
U-235 235.04392 u
Barium-141 140.91441 u

Explanation / Answer

a) 235-141-2 = 92

92-56 = 36

so 30 protons means Zn

92Zn36

b)

M U = MBa + MX + 2 Mn + E

235.04392 = 140.91441 + Mx + 2*1.008665 + 173.2/931.494

Mx= 91.9262 u

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