Nuclear Chemistry -- ANSWERS

Transcription

1 Hoor Chstry Mr. Motro 5-6 Probl St Nuclar Chstry -- ANSWERS Clarly wrt aswrs o sparat shts. Show all work ad uts.. Wrt all th uclar quatos or th radoactv dcay srs o Urau-38 all th way to Lad-6. Th dcay gos as ollows: α, β, β, α, α, α, α, α, β, β, α, β, β, α. a. b. c. d... g. h.. j. k. l U Th Pa U Th Ra R Po Pb B Po Pb B Po Th 8 8 Pa U Th Ra 86 R Po Pb B Po Pb B 8 Po Pb. Wrt balacd uclar quatos or th ollowg procsss: a) bsuth- udrgos bta dcay B b) plutou- ts alpha radato Po Pu 9U c) vaadu-5 udrgos bta dcay V Cr 5 5 3

2 Hoor Chstry Mr. Motro 5-6 d) gold-85 dcays to a rdu sotop 8 79 Au 77Ir Coplt ad balac th ollowg uclar quatos: a) b) c) d) ) S F Mo 35 9 U Ca H p X K P Tc H N Sr. Gallu-67 (t / 78.5 h) s usd th dcal dagoss o crta kd o tuors. I you gst a copoud cotag.5 g o ths sotop, what ass ( llgras) ras your body atr 3 days? (Assu o s xcrtd) Must d ubr o hal-lvs (). hal l h 3 days hal 78.5 h day lvs Usg th orula to d :.5 g g 5. Th ollowg chart shows th dcay o Iro-59 through t. Usg th chart aswr th ollowg qustos: a) What s th ass o Iro-59 at t? As: 3 g b) What s th hal-l o Iro-59? As: 5 yars Mass (g) Dcay o Iro t (days)

3 Hoor Chstry Mr. Motro 5-6 c) How uch 59 F wll b lt o yar? hal l 365 days yar 8. hal 5 days yr lvs 3 g. 85 g 8. d) Wh wll th ass o 59 F rach zro? As: Nvr 6. Th hal-l o Carbo- s 575 yars. A act Egypta uy s oud to b ro th yar 585 BC. What prctag o th orgal aout o Carbo- dos ths uy cota? Total ubr o yars ro 585 BC to today 59 yars hal l 59 yar. 5 hal 575 yars lvs.573 or % 7. Th ass o th uclus o lu- s.5 au. Fd th ass dct or ths uclus. Calculat th uclar bdg rgy or ths uclus. (Us th dvdual ass o all uclos: utro.866 au proto.78 au) Fdg th ass o protos ad utros: ( u) (.866 u). u p Fdg th ass dct: u

4 Hoor Chstry Mr. Motro 5-6 Fdg th uclar bdg rgy (rst covrtg ass dct to klogras): E c.665 u.338 u 8 ( 3. ).5 J 7 8. Th ass o th 56 F uclus s au. Fd th ass dct or ths uclus. Calculat th uclar bdg rgy or ths uclus. Fdg th ass o 6 protos ad 3 utros: ( u) 3(.866 u) 56. u 6 p Fdg th ass dct: u Fdg th uclar bdg rgy (rst covrtg ass dct to klogras): E c.665 u.58 u 8 ( 3. ) J 7 9. Th uclar sso o Urau-35 ca ollow ay drt paths. Th ollowg quatos show two coo paths: U 5T Zr U 56Ba 36Kr 3

5 Hoor Chstry Mr. Motro 5-6 Blow you ca d ass data or th sotops volvd th racto: Isotop Urau-35 Baru- Krypto-9 Tlluru-37 Zrcou-97 Mass (au) a) What s th chag o ass ( ) or ach o th ractos? ass o products ass o ractats Racto () [ ] [ ] T 37 Zr 97 U 35 [ (.866) ] [ ]. u 99 Racto () [ ] [ ] Ba Kr 9 3 U 35 [ (.866) ] [ ]. u 867 b) What s th rgy ( Jouls) rlasd or ach racto? Whch o rlass th ost rgy? Racto (): E c.665 u.99 u 8 ( 3. ).975 J 7 Racto (): E c.665 u.867 u 8 ( 3. ).79 J 7 Racto () producs th ost rgy. Th gatv sg dcats that th rgy was rlasd by th racto (stad o absorbd. c t dots a xothrc procss).

6 Hoor Chstry Mr. Motro 5-6 c) Assug that 6% o a gra sapl o Urau racts as quato # ad th rst as quato # how uch rgy s rlasd? ( g o 35 U.56x atos o 35 U) Bcaus gra o Urau racts,.6 gras (6%) ollow th path o racto () whl. g (%) ollow th path o racto (). Racto (): J.56 ato U.6 g ato U g U J Racto (): J.56 ato U. g ato U g U J c, total rgy rlasd ca b oud as: E total ER acto ER acto J 7.33 J Ths rgy s quvalt to about 8.5 tos o TNT!!!!. (BONUS) A wood artact ro a Chs tpl has a C actvty o.9 couts pr ut as copard wth a actvty o 3.5 couts pr ut or a stadard o zro ag. Fro th hal-l or C dcay, 575 yr, dtr th ag o th artact. Th orato gv couts pr ut s th rat o dcay o th C. Thror, w ar gv th tal ad al rat o dcay. Fro that orato w ca d th rato o th tal ad al ass. Gv that: Rat k Mass Rat Rat k Mass k Mass Mass Mass Whr s th ubr o hal-lvs

7 Hoor Chstry Mr. Motro 5-6 Sc w kow th hal-l o Carbo-, d w ca d how old th artact s. To solv or w d to us logarths. log Rat Rat ( ) Rat log Rat Gv th proprts o logarths, ca co out o th xpot to ultply th log(): log ( ) Rat log Rat Dvdg both sds by log() w obta th xprsso or : log Rat Rat log ( ) Pluggg th valus: 3.5 log.9. 3 hal log ( ) lvs Th ag o th artact s ts th hal-l: Ag hal l y 96. yars