Outline: 4/20/07

Today: Chapter 22 (cont’d)

Nuclear Chemistry- Nuclear Applications…

Fission devices, Radiodating, Nuclear medicine...

Chem seminar today @ 4pm One week to go… Practice final exams online…

Let do some CAPA questions:#8 – A radioactivity counter gives a reading of

385 counts per minute, for a 15.1-mg sample of cobalt(II)chloride, partially enriched with 60Co (half-life = 5.26 yr). What percentage of the cobalt atoms in this sample are 60Co?

Calculate the decays per minute you expect from pure 60CoCl2

Divide 385 cpm by the expected to get percentage…

Let do some CAPA questions:#8 – half-life of 5.26 years:

What is k?

k = 2.508 10-7 1/min

0.693 = k t1/2

k = 0.1318 1/y

Units of 1/min… 1 y / 525,600 min

What is N0?

0.0151 g CoCl2 1 mol/131 g 6.022e23

= 6.941e19 atoms 60Co

Let do some CAPA questions:#8 – N = N0 ekt

t = 1 min

N = 6.940998 e19

N = 6.941e19 exp (-2.508 10-7)

What is N0-N? 1.741e13

Therefore, not much 60Co present: (385 / 1.741e13)100%

= 2.212e-9 %

Nuclear Reactions: Radon Natural series: Uranium 238U + 234Th

234Th + 234Pa

238U

234Pa + 234U 234U + 230Th 230Th + 226Ra 226Ra + 222Rn

222Rn + 218Po

+ 208Pb

Nuclear Reactions: Radon

Nuclear Reactions: Fission

Nucleosynthesis…

Radiodating…

e.g. : If 10.0 g of Kennewick Man bone has 34.6 dpm of 14C, and a present-day 10.0 g bone has 103.7 dpm, how old is Kennewick Man?

N/N0 = e k t or ln(N/N0) = k t ln(34.6/103.7) = k t1/2

t = 9080 yrs

Medical Diagnosis & Treatment:Nuclear Medicine

X-rays/CAT, Tracers, PET, beam therapy, brachytherapy

Why nuclear effects?

High energy, sub-atomic (small) :

highly penetrating

High energy: highly ionizing

What effect does it have on biology?

Mutation….mutagenisis,

Cancer….tumorigenisis.

Does it make atoms radioactive?

No…ionization is a chemical process, not a nuclear process.

Consider Food Irradiation….

Handout: Benign Hamburger

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List of questions to be answered in class on Monday

Everybody has a different selection of questions. Read the “case”. Look for answers in the textbook, look for references in the library/on the web.