please help me with this chem question.....?

Question

Barium crystalizes in a body-centered cubic system with atoms at all lattice points and an edge length of 5.02 angstroms. Calculate its density in g/cm3

Answer 1

Atomic mass of Barium: 137.327g/mol.
A unit cell of a body-centered cubic system holds 2 atoms. hence 3.011x10^23 unit cells would hold 6.022x10^23 atoms or 137.327g of Barium. 3.011x10^23 unit cells would occupy a cube of volume of (5.02x10^(-8))^3*(3.011x10^23) = 38.091cm^3. Thus its density is: 137.327g/38.091cm^3 = 3.605 g/cm^3.