A mammoth skeleton has a carbon-14 decay rate of 0.48 disintegration per minute per gram of carbon (0.48 dis/min • g C). When did the mammoth live? (Assume that living organisms have a carbon-14 decay rate of 15.3 dis/min • g C and that carbon- 14 has a half-life of 5715 yr.)
Ch.20 - Radioactivity and Nuclear Chemistry
Chapter 20, Problem 57
Write the nuclear reaction for the neutron-induced fission of U-235 to form Xe-144 and Sr-90. How many neutrons are produced in the reaction?

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Identify the reactants and products in the nuclear fission reaction: U-235 and a neutron are the reactants, while Xe-144 and Sr-90 are the products.
Write the balanced nuclear equation for the fission reaction: \( ^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{144}_{54}\text{Xe} + ^{90}_{38}\text{Sr} + x \times ^{1}_{0}\text{n} \).
Apply the law of conservation of mass number: The sum of mass numbers on the left side (236) must equal the sum on the right side (234 + x).
Apply the law of conservation of atomic number: The sum of atomic numbers on the left side (92) must equal the sum on the right side (92).
Solve for the number of neutrons \( x \) by ensuring both mass and atomic numbers are balanced.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nuclear Fission
Nuclear fission is a process in which a heavy nucleus, such as uranium-235, splits into two smaller nuclei, along with the release of energy and neutrons. This reaction can be initiated by the absorption of a neutron, leading to a chain reaction that is fundamental in nuclear reactors and atomic bombs.
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Balancing Nuclear Reactions
Balancing nuclear reactions involves ensuring that the total number of nucleons (protons and neutrons) and the total charge are conserved on both sides of the reaction equation. This is crucial for accurately representing the products of a fission reaction, such as the formation of xenon-144 and strontium-90 from uranium-235.
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Neutron Production in Fission
In a typical fission reaction, the splitting of a heavy nucleus not only produces smaller nuclei but also releases additional neutrons. These emitted neutrons can further induce fission in nearby nuclei, perpetuating the reaction. The number of neutrons produced can vary, but in the case of U-235 fission, it typically results in the release of 2 to 3 neutrons.
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Related Practice
Textbook Question
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A rock from Australia contains 0.438 g of Pb-206 for every 1.00 g of U-238. Assuming that the rock did not contain any Pb-206 at the time of its formation, how old is the rock?
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A meteor has a Pb-206:U-238 mass ratio of 0.855:1.00. What is the age of the meteor? (Assume that the meteor did not contain any Pb-206 at the time of its formation.)
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Write the nuclear reaction for the neutron-induced fission of U-235 to produce Te-137 and Zr-97. How many neutrons are produced in the reaction?
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Write the nuclear equation for the fusion of two H-2 atoms to form He-3 and one neutron.
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