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NUCLEAR CHEMISTRY

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NUCLEAR CHEMISTRY Powered By Docstoc
					NUCLEAR CHEMISTRY
    COMPARE THE FOLLOWING
          REACTIONS
l PbCl2   + Li2SO4 à PbSO4 + 2LiCl

l 2Al   + Fe2O3 à 2Fe + Al2O3

l 147N    +   4
                2He   à   17
                             8O   +   1
                                        1H
l   Nuclear Chemistry:
     l The branch of chemistry that deals with nuclear
       reactions, changes in the atomic nucleus
l   Isotopes
     l Are atoms having the same atomic number (# of
       protons) but different mass numbers (# of neutrons)
l   Radioisotope
     l An atom having an unstable nucleus
l   Radioactivity
     l The spontaneous disintegration of an unstable atomic
       nucleus with the accompanying emission of radiation
Properties of each type of
        Radiation
Radiation       Symbols       Charge     Definition
  Alpha     ∝       4
                        2He    +2      Helium nucleus

  Beta          Β   0
                        -1e     -1        Electron

                        +1e
                    0
 Positron                      +1         Positron

 Gamma      γ                   0        High energy
                                       electromagnetic
                                           radiation
   Rules for Writing Equations for
          Nuclear Changes
l Massnumber is conserved in a
 nuclear change

         charge is conserved in a
l Electric
 nuclear change
             Nuclear Equations
l Transmutation
  l change      one element into another
l Types    of Nuclear Reactions
  l Alpha   emission (42He)
    l 21184Po à 42He + 20782Pb
    l 21986Rn à

  l Beta   emission (0-1e)
    l 21083Bi  à 0-1e + 21084Po
    l 22387 Fr à
l Positron    decay (0+1e)
  l 116C   à 0+1e    +   11
                            5B
l K-capture (0-1e)
  l 10046Pd    + 0-1e à 10045Rh
  l 8337Rb
    RULES OF LOGARITHMS
l log   xy = log x + log y

l log   x/y = log x – log y

l log xy    = y log X
l   Half life
l   The length of time necessary for one half an
    amount of a radioactive nuclide to disintegrate

           original mass (1/2)x = final mass

            where x = number of half lives
l   The half life of Ba-131 is 12 days. How much of a
    50.0 g sample will remain after 36 days?
     l 3 half lives   (1/2)3
     l 50.0 g (1/2)3 = x
     l x = 6.25 g
l   If you start with 2.97 x 1022 atoms of Mo-91, how
    many atoms will remain after 62.0 minutes? The half
    life of Mo-91 is 15.49 minutes.
     l 4 half lives  (1/2)4
     l 2.97 x 1022 (1/2)4 = x
     l x = 1.86 x 1021 atoms
l What is the half-life of a radioactive
 isotope if a 100.0g sample decays to 12.5
 g in 24.0 hours?
         original mass (1/2)x = final mass
              100.0 g (1/2)x = 12.5 g
                   (1/2)x = 0.125
               log (1/2)x = log 0.125
              x log (1/2) = log 0.125
                   x = 3 half lives
                 24.0 hrs/3 = 8 hrs
l How  old is a bone if it presently contains
 0.0625g of C-14, but it was estimated to
 have originally contained 1.000g of C-14
 (half life = 5730 yr)?
            original mass (1/2)x = final mass
                1.000g (1/2)x = 0.0625 g
                      (1/2)x = 0.0625
                  log (1/2)x = log 0.0625
                 x log (1/2) = log 0.0625
                       x = 4 half lives
             4 ( 5730 years) = 23,000 years

				
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