PLEASE CHECK MY ANSWERS! CHEM EASY problem #26

Chemistry
Tutor: None Selected Time limit: 1 Day

Feb 17th, 2015

  1. Face Centered Cubic

  2. Coordination number of 12

  3. 8 unit cells

  4. 0 unit cells (just with an adjacent atom)

  5. 4 atoms per unit cell

  6. Mass of unit cell = mass 4 Al atoms = (195.08)(g/mol)(1mol/6.022x1023atoms)(4 atoms/unit cell) = 12.96 x 10-22 g/unit cell

    1 amu = 1.66054 x 10-24 g

    Thus, 12.96 x 10-22 g/unit cell / 1.66054 x 10-24 g = 780.47 amu

  7. Edge length 3.924 A. Thus, the Volume unit cell = A3 = (3.924x10-8cm)3 = 60.42x10-24 cm3/unit cell = 60.42 A3 ( since 1 A3 = (10-8 )3 cm3 )

  8. 74%

  9. 100-74 = 26%

  10. As we know, total volume is 100 % and it is 60.42 A3

    Then, 74 % (volume of atoms only) would be: 74 x 60.42 A3 / 100 = 44.71 A3

  11. V = 4/3 πr

    Thus, r = (V/ (4/3 π))1/3 = (3x44.71/4 π)1/3 = 2.202 A

  12. Density = m/V = 780.47 amu /60.42 A3

    1 amu = 1.66054 x 10-24 g

    Thus, 760 amu = 12.96 x 10-22 g, since in order to convert to grams: 760 amu x 1.66054 x 10-24 g / 1 amu = 12.96 x 10-22 g

    1 A3 = (10-8 )3 cm3

    Thus, 60.42 A3 in cm3 is = 60.42 A3 x (10-8 )3 cm3 / 1 A3 = 60.42x10-24 cm3

    Density = m/V = 12.96 x 10-22 g/60.42 A3 = 12.96 x 10-22 g / 60.42x10-24 cm3 = 21.45 g/ cm3


Feb 17th, 2015

i think your 2 and 4 is wrong? can you check? 

Feb 17th, 2015

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