Final answer:
The mass of a Uranium-235 nucleus is less than the sum of the masses of its fission products and neutrons due to the mass defect. A Uranium-235 nucleus has 92 protons and 143 neutrons. The energy released in the fission reaction can be measured in MeV by converting the mass difference using the conversion factor.
Step-by-step explanation:
The mass of a Uranium-235 (235 U) nucleus is less than the combined mass of a Barium-141 (141 Ba), Krypton-92 (92 Kr), and two neutrons when they are separated from each other. This is due to the mass defect, which arises from the binding energy that holds the nucleus together. In this fission reaction, the difference in mass is converted into energy as described by Einstein's E=mc^2.
An isotope of uranium with atomic number 92 has a mass number of 235. The number of protons in the nucleus is 92, and the number of neutrons can be calculated by subtracting the atomic number from the mass number, which gives us 143 neutrons.
Regarding the energy released, when assuming that the mass of 235U is 235.04 u, the mass of 141Ba is 140.91 u, the mass of 92Kr is 91.93 u, and the mass of a neutron (n) is 1.01 u, the energy released in the fission reaction can be converted from atomic mass units (amu) to energy in joules using the conversion factor of 1 u = 931.5 MeV/c^2, and thus the value of 2.689 × 10-11 joules can be expressed in mega electron volts (MeV) using this conversion.