The cubic unit cell of Al (molar mass 27 g `"mol"^(-1)` ) has an edge length of 405 pm. Its density is `2.7gcm^(-3)` . The cubic unit cell is :

Options

A. body centred
B. primitive
C. edge centred
D. face centred

Answer

D

Explanation

`d = (Z xx M)/(a^3 xx N_A)`
`2.7 = (Z xx 27)/((405 xx 10^(-10))^(3) xx (6.02 xx 10^(23)))`
or `Z = (2.7 xx (405 xx 10^(-10))^(3) xx 6.02 xx 10^(23))/(27) = 4`
`:.` Lattice is fcc .