Question

4. The energy released by the fission of one atom of uranium-235 is 3.2 x 10 R J. The energy released by the atomic bomb dropped at Hiroshima was estimated to be the equivalent of 18 140 t of dynamite or 8.0 × 1013 J (a) How many atoms of uranium-235 underwent fission? (b) What mass of uranium-235 was converted into energy?

Answer 1

here we use energy mass equivalence formula to solve the problem...

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a) no of atoms = n = 8 times 10^13 J/32 times 10^-8 J = 2.5 times 10^21 atoms b) E = mc^2 or, 8 times 10^13 J = m(3 times 10^8 m/s)^2 or, m = 8.89 times 10^-4 kg