Question

A metal $M$ crystallizes into two lattices :- face centred cubic (fcc) and body centred cubic (bcc) with unit cell edge length of $20$ and $25 \,\mathring{A}$ respectively The ratio of densities of lattices fcc to bcc for the metal $M$ is ___(Nearest integer)

Answer 1

The correct answer is 4.
d=NA​a3Z×M​
dBCC​dFCC​​=NA​×(2.5)32×Mw​​NA​×(2)34×Mw​​​=3.90