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The number of nuclei in 1 gram of copper (Cu)

  1. Apr 30, 2014 #1
    [itex]^{62}Cu[/itex] is 61.932586 amu. I would like to know how many exposed nuclei are in 1.0 gram of [itex]^{62}Cu[/itex]. I have two calculations below, hopefully one of them is correct...

    Method 1.

    1.0 gram [itex]^{62}Cu[/itex] x [itex]\frac{1 kg}{1000 g}[/itex] x [itex]\frac{1 amu}{1.660566 x 10^{-27}kg}[/itex] x [itex]\frac{1 mole ^{62}Cu}{61.932586 amu}[/itex] x [itex]\frac{6.022 x 10^{23} nuclei}{1 mole ^{62}Cu}[/itex] = 5.8555 x 10[itex]^{45}[/itex] [itex]^{62} Cu[/itex] nuclei

    Method 2.

    1.0 gram [itex]^{62}[/itex]Cu x [itex]\frac{1 mole ^{62}Cu}{61.932586 grams}[/itex] x [itex]\frac{6.022 x 10^{23} nuclei}{1 mole ^{62}Cu}[/itex] = 9.723 x 10[itex]^{21}[/itex] [itex]^{62}Cu[/itex] nuclei
  2. jcsd
  3. Apr 30, 2014 #2


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    Science Advisor
    Gold Member

    As an approximation you can consider one gram of matter to contain Avogadro's number worth of nucleons; since Cu-62 has 62 nucleons, the number of nuclei is Av./62 = 9.713e21.

    So your method 2 is correct. Can you see what went wrong in the first method?
  4. Apr 30, 2014 #3


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    Staff: Mentor

    In Method 1 the conversion factor 1 mole 62Cu = 61.932586 amu is incorrect. In method 2 you have the correct conversion factor, 1 mole 62Cu = 61.932586 g.

    61.932586 amu is the mass of one atom of 62Cu.

    [UltrafastPED slipped in before I finished typing!]
  5. Apr 30, 2014 #4
    jtbell, thanks! I don't think I could have arrived at that conclusion on my own...
  6. Apr 30, 2014 #5
    :smile: UltraFastPED, thanks as well for your quick response... appreciate the help, as well as the rule of thumb you mentioned
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