Question

Silver forms ccp lattice and X-ray studies of its crystal show that the edge length of its unit cell is 408.6 pm. Calculate the density of silver (Atomic wt. = 107.9u).

Answer 1

Silver forms cubic close packing (ccp) , therefore the number of silver atoms per unit cell z=4

Molar mass of silver M=107.9 gmol⁻¹ = 107.9×10⁻³kgmol⁻¹

Edge length of unit cell a=408.6 pm = 408.6×10⁻¹²

Density d=(z.M)/(a³.N_A)

d=4×(107.9×10⁻³kgmol⁻¹)/(408.6×10⁻¹²m)³(6.022×10²³mol⁻¹)

=10.5×10³kgm⁻³

d=10.5gcm⁻³