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Chapter 31: Q20 CQ (page 1148)
Radioactivity depends on the nucleus and not the atom or its chemical state. Why, then, is one kilogram of uranium more radioactive than one kilogram of uranium hexafluoride?
Uranium is more radioactive than uranium hexafluoride, which costs \(1\;{\rm{kg}}\).
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Confirm that charge, electron family number, and the total number of nucleons are all conserved by the rule for α decay given in the equation\(_Z^A{X_N} \to _{Z - 2}^{A - 4}{Y_{N - 2}} + _2^4H{e_2}\). To do this, identify the values of each before and after the decay.
(a) Write the complete\({{\rm{\beta }}^{\rm{ - }}}\]decay equation for\({}^{{\rm{90}}}{\rm{Sr}}\], a major waste product of nuclear reactors. (b) Find the energy released in the decay.
Armor-piercing shells with depleted uranium cores are fired by aircraft at tanks. (The high density of the uranium makes them effective.) The uranium is called depleted because it has had its \(^{{\rm{235}}}{\rm{U}}\)removed for reactor use and is nearly pure\(^{{\rm{238}}}{\rm{U}}\). Depleted uranium has been erroneously called non-radioactive. To demonstrate that this is wrong:
(a) Calculate the activity of \(60.0\;\,{\rm{g}}\)of pure\(^{{\rm{238}}}{\rm{U}}\).
(b) Calculate the activity of \(60.0\;\,{\rm{g}}\)ofnatural uranium, neglecting the\(^{{\rm{234}}}{\rm{U}}\) and all daughter nuclides.
Confirm that charge, electron family number, and the total number of nucleons are all conserved by the rule for β- decay given in the equation \(_Z^A{X_N} \to _{Z - 1}^A{Y_{N + 1}} + {\beta ^ - } + {v_e}\). To do this, identify the values of each before and after the decay.
Neutrinos are experimentally determined to have an extremely small mass. Huge numbers of neutrinos are created in a supernova at the same time as massive amounts of light are first produced. When the 1987A supernova occurred in the Large Magellanic Cloud, visible primarily in the Southern Hemisphere and some 100,000 light-years away from Earth, neutrinos from the explosion were observed at about the same time as the light from the blast. How could the relative arrival times of neutrinos and light be used to place limits on the mass of neutrinos?
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