Precise measurements give the following masses: nuclide mass particle mass 238.0

Question

Precise measurements give the following masses: nuclide mass particle mass 238.05079 u 1.0086649 u 0 234 90 Th 234.04360 u 0 le 5.4858 × 10-4 u 0 e 5.4858 x 10 u He 4.00260 u Now consider the following nuclear reaction: 238 92 234 90 4 released absorbed Is energy released or absorbed by this reaction? neither released nor absorbed I need more information to decide If you said energy was released or absorbed, calculate how much energy is released or absorbed Give your answer in both kJ/mol and MeV. Round each of your answers to 3 significant digits kJ/mol MeV Note: take particular care to keep enough digits in any intermediate calculation, and use enough digits in any scientific constants you need, since the data with which you are working are very precise.

Explanation / Answer

Energy is released by this reaction.

Mass before reaction = 238.05079

Mass after reaction = 234.04360 + 4.00260 = 238.0462

Mass defect = 238.0462 - 238.05079

= - 0.00459 amu x 1.66 x 10^-27 kg/amu

m = - 7.6194 x 10^-30 kg

Energy released per mol = m x c2

= - 7.6194 x 10^-30 kg x (299792458 m/s)^2

= - 6.8479 x 10^-13 J/mol x 1kJ/1000 J

= - 6.8479 x 10^-16 kJ/mol

E = (6.8479 x 10^-13 J/mol) / (1.60 x 10^-19 J/mol-eV)

= - 4.279 x 10^6 eV x 10^-6 MeV/eV

= - 4.28 MeV

Negative sign shows that the heat is released

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