Question

An element crystallizes in fee lattice with cell edge 250 pm. Calculate the density of an element. (At. Mass = 90.3)

Options

• 19.20 g cm^-3

• 38.40 g cm^-3

• 48.40 g cm^-3

• 23.12 g cm^-3

Answer 1

38.40 g cm^-3

Explanation:

a = 250 pm = 2.5 × 10^-8 cm

M = 90.3 g mol^-1, n = 4 (for fcc cell) 

`rho = ("n" xx "M")/("a"^3 xx "N"_"A")`

`= (4 xx 90.3)/((2.5 xx 10^-8)^3 xx 6.022 xx 10^23)`

∴ ρ = 38.40 g cm^-3