this is a wiley plus problem and there is no reading lesson with this section so im not sure how to approach this question:

The element iridium has ccp packing with a face-centered cubic unit cell. The density of Ir is 22400 kg/m3. Calculate the volume (cm3) of the unit cell of iridium.

The molar mass of iridium is 192.22 g/mol

Thanks!

1 answer

mass = volume x density; therefore,
volume = mass/density. You know the density; therefore, we need to determine the mass of a unit cell.
An atom of Ir has a mass of 192.22/6.022 x 10^23. There are 4 atoms/unit cell which makes the mass of a unit cell then
4 x 192.22/6.022 x 10^23. Substitute into the first equation above and calculate volume. If you want the volume in cc, you must have the density in g/cc. 22,400 kg/m^3 = 22.4 g/cc.