Iron is a solid phase of iron still unknown to science. The only difference between it and ordinary iron is that Iron forms a crystal with an fcc unit cell and a lattice constant . Calculate the density of Iron.

The question is incomplete. The complete question is :

Iron β is a solid phase of iron still unknown to science. The only difference between it and ordinary iron is that Iron β forms a crystal with an fcc unit cell and a lattice constant, a = 0.352 nm. Calculate the density of Iron β.

Solution :

The density is given by :

        ..................(i)

Here, Z = number of atoms in a unit cell

         M = atomic mass

          = Avogadro's number =

          a = edge length or the lattice constant

Now for FCC lattice, the number of atoms in a unit cell is 4.

So, Z = 4

Atomic mass of iron, M = 55.84 g/ mole

Given a  = 0.352 nm = cm

From (i),

Therefore, the density of Iron β is .