Energy changes in nuclear reactions

The energies associated with nuclear reactions can be considered with the aid of Einstein s celebrated equation relating mass and energy  

The mass changes in chemical reactions are too small to detect. For example, the mass change associated with the combustion of 1 mol of CH4 (an exothermic process) is —9.9 X 10 g. Because the mass change is so small, it is possible to treat chemical reactions as though mass is conserved. 

The masses of the nuclei are IfU, 238.0003 amu loTh, 233.9942 amu and fHe, 4.0015 amu. The mass change. Am, is the total mass of the products minus the total mass of the reactants. The mass change for the decay of I mol of uranium-238 can then be expressed in grams  

The fact that the system has lost mass indicates that the process is exothermic. All spontaneous nuclear reactions are exothermic. 

The energy change per mole associated with this reaction is 

Why are the energies associated with nuclear reactions so large, in many cases orders of magnitude larger than those associated with nonnuclear chemical reactions The answer to this question begins with Einstein s celebrated equation from the theory of relativity that relates mass and energy  

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However, it must be recognized that there is an important difference between the energy changes involved in nuclear reactions and those in ordinary chemical changes. In relation to the masses of matter that undergo transformation, the energy changes in nuclear reactions are enormous in comparison with those which accompany ordinary chemical reactions. 

The energy changes in nuclear reactions are much larger. This can be seen if we use the relationship between electron volts and joules (or calories) in Appendix IV, and observe that... 

The energy changes in nuclear reactions are much greater than those associated with chemical reactions. This is because there are mass changes in nuclear processes. Mass and energy are related by the Einstein equation... 

We recognize that energy changes in nuclear reactions are related to mass changes via Einstein s equation, = mc. The nuclear binding energy of a nucleus is the difference between the mass of the nucleus and the sum of the masses of its nucleons. 

Energetics of Nuclear Reactions— The energy changes in nuclear reactions are a consequence of Einstein s discovery of a mass-energy equivalence (equation 25.19). 

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