L42S07_ Radiochem_Nuclides-2 05-02-07

Nitsche 2 21na 23na 3 21ne 23mg l42 6 2004 mkubinec

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Unformatted text preview: rgy (in eV) is released eV) when a positron and electron annihilate each other? Mass of the electron and positron is 5.486 x 10-4 amu 1) ~1 eV 2004 M.Kubinec, H.Nitsche 2) ~103 eV 3) ~106 eV L42-8 ChemQuiz 41.4 Solution How much energy (in eV) is released when a positron eV) and electron annihilate each other? E= mc2 For 1 e-, eE= (5.486 X 10-4 amu)(931.5 MeV/amu)= ~5X105 eV MeV/amu)= For an e- and an e+, E = 2 X 5X105 eV = ~106 eV e- 1) ~1 eV 2004 M.Kubinec, H.Nitsche 2) ~103 eV 3) ~106 eV L42-9 Summary 2004 M.Kubinec, H.Nitsche L42-10 2004 M.Kubinec, H.Nitsche 3 CHEM 1A L42:"RadiochemPrinciples" 90 38 100 Decay Rate Sr Half-life 0 90 -1 N (number of atoms) e + 39 Y 1 Curie (Ci) = 3.7 x 1010 disintegrations s-1 (Ci) exponential decay: Nt=Noe-t 29 y N half-life = t1/2 = 29 y: t1/2 = ln2/ ln2/ half10 half-lives ~ 99.9% decay half- 20 40 60 80 100 years 120 L42-11 2004 M.Kubinec, H.Nitsche ChemQuiz 42.1 A tritium luminescent watch manufactured in 1983 retains of its original intensity. intensity. What is the half life of tritium? 1) ~ 6 y 2004 M.Kubinec, H.Nitsche 2) ~ 12 y 3) ~ 24 y L42-12 ChemQuiz 42.2 Approximately what year will there be less than 0.1% of the tritium in the watch? 1) 2050 2004 M.Kubinec, H.Nitsche 2) 2100 3) 2500 L42-14 2004 M.Kubinec, H.Nitsche 4 CHEM 1A L42:"RadiochemPrinciples" Lecture Complete 2004 M.Kubinec, H.Nitsche L42-16 2004 M.Kubinec, H.Nitsche 5...
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