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Homework Help: Magnetic Susceptibility and Unpaired electrons

  1. Mar 2, 2017 #1
    1. The problem statement, all variables and given/known data
    I'm am trying to find out the magnetic susceptibility,XM in order to calculate the number of unpaired electrons in Mn(acac)3 via the Evans Method

    2. Relevant equations
    XM = (477) Δv/(Qv1C)
    XM= X'm+ XM(metal)+ XM (ligands)
    Where X'M is the magnetic susceptibilty of just the unpaired electrons.
    Δv is the frequency difference between the two chloroform peaks, 648.2 MHz (7.2722 ppm-5.6517 ppm)*400 MHz
    Q=2 because a superconducting NMR was used
    v1 is the frequency of the NMR, 400MHz
    and c is the molarity of the solution used, 0.0948M
    X'MT=(1/8)n(n+2) where n is number of unpaired electrons
    3. The attempt at a solution
    The XM I calculated is 4179.1878. I have nothing to base the accuracy of this off of.
    the XM (metal) = 511. THis was for elemental Mn. I couldn't find anything for Mn(III) so this might be the problem. And from the lab manual the XM(ligands) is 3*52
    Solving for X'M I got 3512.1878
    This gives an unpaired electron count of of nearly 3,000 so this cannot be correct.

    Any help is greatly appreciated.
  2. jcsd
  3. Mar 3, 2017 #2


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    Science Advisor

    Δν > ν1? Looks like you multiplied 1.6205*400. What about the "ppm"?
  4. Mar 3, 2017 #3
    1.6205 is the ppm. That's what the lab manual says to do.

    EDIT: I see. the ppm x 400 MHz= Hz. I wasn't reading carefully. I'll see if this fixes things
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