Question

Copper whuch crystallises at fcc has density 8.93 calculate edge length

Answer 1

d=z×Ma3×NAd=z×Ma3×NA

No. of atoms in fcc lattice z=4

d=4×63.5mol−1(3.61×10−8cm)3×(6.02×1023mol−1)d=4×63.5mol−1(3.61×10−8cm)3×(6.02×1023mol−1)

Atomic mass of unit cell =4×63.56.02×10234×63.56.02×1023g

⇒4.22×10−22⇒4.22×10−22g

Density =Mass of unit cellVolume of unit cellMass of unit cellVolume of unit cell

⇒4.22×10−2247.4×10−24cm2⇒4.22×10−2247.4×10−24cm2

⇒8.9gcm−3⇒8.9gcm−3

Which is in close agreement with the measured value.

Density = Mass of unit cell/Volume of unit cell

8.93=(4×63.5)/(a3×6.02×1023).8.93=(4×63.5)/(a3×6.02×1023).

a3=47.24x10−24a3=47.24x10−24

=360pm=360pm