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Homework Help: Density of NaCl

  1. May 23, 2010 #1
    1. The problem statement, all variables and given/known data

    Calculate the density of crystalline NaCl, given that NaCl has a face-centred cubic lattice with a dimension a = 5.64A.

    2. Relevant equations

    1/8 Cl ion at each corner, 1/2 Cl ion on each face. 1 whole Na in the center, 1/4 Na ion along each edge.

    3. The attempt at a solution

    ok where do i begin
     
  2. jcsd
  3. May 23, 2010 #2
    Is your question full?
    For a FCC structure: corner atoms contribute only 1/8 and face-centered atoms contribute 1/6. So for a FCC system total number of atoms = 8(1/8) + 6(1/2) =4.
    But which is corner atom and which is face-centered atom ?
    Only idea comes to my mind is:
    you should take 'a' as distance between two nearby Cl or Na atom. Then find the kg of NaCl single unit using 'mole' and 'Avogadro' stuff. Also you know volume. So you can compute density.
    Hope this help
     
    Last edited: May 23, 2010
  4. May 23, 2010 #3

    Astronuc

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    Given - "1/8 Cl ion at each corner, 1/2 Cl ion on each face. 1 whole Na in the center, 1/4 Na ion along each edge." - how would one determine the total atomic mass in the unit cell?

    Then given the mass, how would one determined the density?
     
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