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Which statement about nuclear fission is correct?

1. About 0.1% of the mass is transformed into energy.
2. The major part of the energy released in fission appears as heat.
3. During the fission of U-235, nearly 200 eV of energy is released.
4. On average, one neutron is emitted in each fission of U-235.

Correct answer: About 0.1% of the mass is transformed into energy.

Solution

In U-235 fission about 200 MeV is released per nucleus; as a fraction of its rest energy (235 x 931 MeV) this is ~0.09% ~ 0.1% of the mass converted to energy. (U-235 releases ~200 MeV not 200 eV, and emits ~2.5 neutrons on average, not one.)

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