The `gamma`-form of iron has fcc structure (edge length 386 pm) and `beta`-form has bcc structure (edge length 290 pm). The ratio of density in `gamma`-form and `beta`-form is

Options

A. 0.8481
B. 1.02
C. 1.57
D. 0.6344

Answer

A

Explanation

`Z_(eff)` for fcc = 4 and for bcc = 2/unit cell
`rho_(gamma)/rho_(beta)=rho_("fcc")/rho_("bcc")=(Z_("eff(fcc)"))/(Z_("eff(bcc)"))xx((a_("bcc"))/a_("fcc"))^(3)=4/2xx(290/386)^(3)=0.8481`