The face centred cubic cell of platinum has a length of 0.392nm. Calculate the density of platinum (g/cm3):(Atomic weight:Pt=195)

The face centred cubic cell of platinum has a length of 0.392nm. Calculate the density of platinum (g/cm3):(Atomic weight:Pt=195)

(A)20.9

(B)20.4

(C)19.6

(D)21

Solution=

Density=Z×Mw/Na×a3

Here Z = No. of atoms in fcc crystal = 4

Na= Avagadro No. =6×1023

a=Edge length

Mw=Molecular weight of crystal

Density=4×195Na×(0.392×10−7)3

Density=21gcm