an element A crystallises in fcc structure . 200g of this element has 4.12*10^24 atoms. the density of A is 7.2g/cm^3.calculate the edge length of the unit cell

Asked by Akshaya Parthasarathy | 2nd Jul, 2011, 12:00: AM

Expert Answer:

Let length of each edge = a cm

     volume of  unit cell =a3 cm3

 

Mass of each atom = 200 / (4.12 x 1024)

                           =48.54 x 10-24    g

 For fcc   Z =4

 Mass of unit cell  = 4 x 48.54 x 10-24

                         = 194.16 x10 -24 g

 

Density =mass / volume

 7.2 =194.16  x 10-24/a3

a3 =194.16 x10-24/ 7.2 =26.97 x 10-24

a = 2.999 x10-8 cm

   =299.9 pm

Answered by  | 4th Jul, 2011, 11:08: AM

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