A metal crystallizes into two cubic phases, face-centred cubic and body-centred cubic, which have unit cell lengths `3.5` and `3.0 A`, respectively. Calculate the ration of densities of fcc and bcc.

Explanation

Denstiy ` (p) = ( Z xx M)/(a^(3) xx N_(0)) `
For Z = 4, a = 3.5 Å = 3.5 Å = 3.5 ` xx 10^(-8)` cm .
` p_("fcc")= (4xxM) /((3.5 xx 10^(-8))xx N_(0)) `
for bcc, Z =2 , a = 3.0 Å = 3.0 ` xx 10^(-8)` cm
`p_("bcc")= ( 2xx M)/((3.0 xx10^(-8))^(3) xx N_(0)) therefore p_("fcc")/p_("bcc") = ( 4xx (3.0 xx 10^(-8))^(3))/(2xx (3.5 xx10^(-8))^(3) ) =1.259`