1 / 15

Outline: 4/18/07

Outline: 4/18/07. Avg: 7.2. Pick up Quiz 9 – from me Special seminar Wednesday 7:30pm & Thursday 3pm Last two seminars: Friday @ 4pm. Today: Chapter 22 (cont’d). Nuclear Chemistry - Common decay calcs - Biological interactions. Let do some CAPA questions:.

odessa
Download Presentation

Outline: 4/18/07

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Outline: 4/18/07 Avg: 7.2 • Pick up Quiz 9 – from me • Special seminar Wednesday 7:30pm & Thursday 3pm • Last two seminars: Friday @ 4pm Today: Chapter 22 (cont’d) Nuclear Chemistry - Common decay calcs - Biological interactions

  2. Let do some CAPA questions: • Mono-isotopic: only one isotope • It weighs: 26.982 g/mol (per. table) #4 – What’s the binding energy of 27Al? • Add up the masses of the protons & neutrons & electrons, and subtract the total mass of the individual constituents from the actual mass of the isotope.

  3. Let do some CAPA questions: How many protons? • 13 #4 – What’s the binding energy of 27Al? How many neutrons? • 14 How many electrons? • 13 • Table 22-1 (p. 944): 131.007276 + 141.008665 + 130.000549 = 27.223 g/mol • Difference: =26.982 - 27.223 g/mol =-0.241 g/mol  8.988e10 kJ/g = -2.17e10 kJ/mol

  4. How does this compare to chemical energies? • Explosion of tri-nitro-toluene (TNT) has a DH of 1026 kJ/mol… • The amount of energy used to hold together 1 mole of Al nuclei is: 21700000000 kJ/mol…

  5. Binding Energy per Nucleon

  6. Let do some CAPA questions: • 1.0-1.5 Check proton-to-neutron ratio #8 – Which are the stable isotopes? Check for odd-odd p & n Check for heavies (Z>83) Check for artificial elements (Tc, 3H)

  7. 0.143 mol 14C  6.022e23 atoms/mol • = 8.60e21 atoms 14C Worksheet #13 - Question 2 • 0.02% of 1000g = • 0.2 g 14C • 0.2 g  1mol/14g = 0.143 mol 14C • N/N0 = 7.65e20 / 8.60e21 = 0.0889 • ln (0.0889) = - k t • - 2.42 = - 1.209 × 10-4 yr-1 t • t = 20,000 yr

  8. N = ? • N = 7.65e20e- kt • 7.65e20 e - 1.209 × 10-4 (1/52) Worksheet #13 - Question 3 • 7.65e20 14C atoms = • N0 • t = 1/52 yr • N = 7.64998e20 N- N0 = 1.78e15

  9. a b g Why a thin layer? High energy, sub-atomic (small) : highly penetrating High energy: highly ionizing

  10. What effect does it have on biology? Penetrating, ionizing…..

  11. Why is too much radiation bad for living things?

  12. case 2: DNA - single ionization  radiation ionizes & breaks the strand on one side - but the DNA repairs itself case 1: a cell  radiation ionizes the cell wall or other parts and kills the cell

  13. case 3: DNA - multiple ionization   rearrangements are possible - a mutation occurs radiation ionizes & breaks the strand - DNA fragments

  14. case 4: DNA - multiple ionization Since break-points are far away, DNA repairs itself   radiation ionizes & breaks the strand

  15. What affect does it have on biology? Mutation….mutagenisis, Cancer….tumorigenisis. Does it make atoms radioactive? No…ionization is a chemical process, not a nuclear process.

More Related