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General Chemistry Principles, Patterns, and Applications, 2011

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E X A M P L E 9<br />

Calculate the amount of energy (in electronvolts per atom <strong>and</strong> kilojoules per mole) released when the<br />

neutron-induced fission of 235 U produces 144 Cs, 90 Rb, <strong>and</strong> two neutrons:<br />

U92235 + n01® C55144s + R3790b + 2n01<br />

Given: balanced nuclear reaction<br />

Asked for: energy released in electronvolts per atom <strong>and</strong> kilojoules per mole<br />

Strategy:<br />

A Following the method used in Example 7, calculate the change in mass that accompanies the reaction.<br />

Convert this value to the change in energy in electronvolts per atom.<br />

B Calculate the change in mass per mole of 235 U. Then use Equation 20.29 to calculate the change in energy<br />

in kilojoules per mole.<br />

Solution:<br />

A The change in mass that accompanies the reaction is as follows:<br />

Dm = massproducts - massreactants = mass(C55144s + R3790b + n01)<br />

-mass U92235 = (143.932077 amu + 89.914802 amu +1.008665<br />

amu)- 235.043930 amu = -0.188386 amu<br />

The change in energy in electronvolts per atom is as follows:<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

1885

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