Q11 of 26 Page 1

An element crystallizes in a structure having a fcc unit cell of an edge 200 pm. Calculate the density, if 200 g of this element contains 24 x 1023atoms.

Given:


Edge length (a) = 200 pm = 200 × 10-12 m =2 × 10-8 cm


No. of atom per unit cell in a fcc crystal lattice (Z) = 4


Mass (m) = 200g


Mass of 24 × 1023 atoms = 200gm


Mass of 4 atoms= = 33.33 × 10-23


Volumes of unit cell ( a3 )= (2 × 10-8 )3


= 8 × 10-24 cm3


Density (ρ ) = Mass/volume


= = 41.62 g/cm3


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