A metal of atomic mass $64 g mo l^{- 1}$ crystallises in a face-centred cubic lattice with edge length $360 pm$ . Its density in $g c m^{- 3}$ is (take $N_{A} = 6.022 \times 1 0^{23} mo l^{- 1}$ )

Answer: A

ρ = \frac{ZM}{N _{A} a ^{3}}

with

Z = 4

a = 3.60 \times 1 0^{- 8} cm

ρ = \frac{4 \times 64}{6.022 \times 1 0 ^{23} \times ( 3.60 \times 1 0 ^{- 8} ) ^{3}} = 9.11 g c m^{- 3}