Q.
A solid having density of 9×103kgm−3 forms face centred cubic crystals of edge length 2002pm. What is the molar mass of the solid? [ Avogadro constant ≃6×1023mol−1,π≃3]
Formula for density,
Density, d=a3×NAZ×M
where, d= density of the unit cell M= Molar mass of the molecule a3= volume of the unit cell NA= Avogadro number
Here, for FCC unit cell, Z=4
Subsituting the values we get, 9×103=(2002×10−12)3×6.0×10234×M ⇒M=0.0305kg.mol−1