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Calculating Molar Mass from a BCC

  1. Feb 2, 2009 #1
    1. The problem statement, all variables and given/known data

    An element has bcc packing with a body-centered cubic unit cell. Its density is 862 kg/m^3 and the unit cell volume is 1.51 x 10-28 m^3. Calculate the molar mass (g/mol) of the element to three significant figures.

    2. Relevant equations

    Known: D= 862 kg/m^3, V=1.51 x 10-28 m^3 , MM=??

    3. The attempt at a solution

    Ok the correct answer is 39.2, but I don't know how to arrive to that answer.

    (862kg/m^3)(1.51e-28m^3)(1000g/1kg)(6.022e23atoms/1mol)(1/2 atoms)
    (0.68) but instead I get 26.6504.

    The 0.68 is the density packing.
  2. jcsd
  3. Feb 2, 2009 #2


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    Staff: Mentor

    Are you sure it is relevant to the question?
  4. Feb 2, 2009 #3
    ah, htat wasn't required, thanks
  5. Feb 3, 2009 #4


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    Staff: Mentor

    The real question is: do you understand what you did and why?
  6. Feb 3, 2009 #5
    Yes, I pretty much converted to the proper units I needed, the only problem was getting the right units.
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