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Calculating Density Bravais Lattices

  1. Jan 29, 2014 #1
    1. The problem statement, all variables and given/known data
    Calculate the density of Iron with the following information.
    side length = 2.86 angstroms
    Atomic weight = 55.85
    Body centered cubic, so 2 atoms per unit cell.

    2. Relevant equations
    Density = ((# of atoms)(Atomic Weight)) / ((volume of cell)/Avogadro's Number))

    3. The attempt at a solution
    So this should be really easy, but I can't get the correct number with this formula, what am I doing wrong?

    Atomic Weight of 55.85 means a mass of 9.274117017e-26 kg.
    Side Length of 2.87 angstroms mean that the side length is 2.87E-10 Meters.
    Cube this side length to get the total volume.

    so using the formula...
    (2)(9.274117E-26) / (2.87E-10)^3*(6.022^23) = 1.302915E-20 kg/m^3.. which is obviously very incorrect... Help meh?
  2. jcsd
  3. Jan 29, 2014 #2


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    Science Advisor
    Homework Helper

    You already converted the atomic weight to mass per atom. I don't see why you are dividing by Avogadro's number again. Density is just mass/volume.
    Last edited: Jan 29, 2014
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