1) An injection containing 17.0 pg 10 5B was injected into a patient suffering f
ID: 1477547 • Letter: 1
Question
1)
An injection containing 17.0 pg 10 5B was injected into a patient suffering from a brain tumor. The patient was irradiated by a neutron gun at the site of the tumor. Calculate the amount of energy released in megaelectronvolts given that 931 MeV is released for each 1 amu mass defect.
To calculate the energy released, consider the isotopic masses as follows:
Express your answer in megaelectronvolts to three significant figures.
2)
A particular smoke detector contains 1.75 ?Ci of 241Am, with a half-life of 458 years. The isotope is encased in a thin aluminum container. Calculate the mass of 241Am in grams in the detector.
3)
A radioactive sample contains 1.65 g of an isotope with a half-life of 3.9 days. What mass of the isotope will remain after 5.5 days? (Assume no excretion of the nuclide from the body.)
4)
Why does a nuclide with an N/Z ratio that is too low tend to undergo positron emission or electron capture?
Why does a nuclide with an N/Z ratio that is too low tend to undergo positron emission or electron capture?
Element or particle Isotopic mass(amu) 10 5B 10.0129 neutron 1.0086 73Li 7.0160 alpha particle 4.0026
Explanation / Answer
(1) the nuclear reaction is given by
5B10 + on1 ------> 3Li7+2He4
Mass defect per Boron atom= (10.0129+1.0086)-(7.0160+4.0026)=0.0029 amu
number of born atoms in 17pg=(17x10-12/10.0129) * 6.022x1023=1.02242x1012 atoms
Total energy released= 0.0029*1.02242x1012*931=2.76x1012 MeV
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