An element crystallising in body centred cublic lattice has edge length of 500 pm. If the density is 4 g `cm^(-3)`, the atomic mass of the element `("in g mol"^(-1))` is (consider `N_(A)=6xx10^(23))`

Options

A. 100
B. 250
C. 125
D. 150

Answer

D

Explanation

`rho = (Z xx M)/(a^3 xx N_A)`
For bcc, `Z = 2 , a = 500 xx 10^(-10) cm`
`d = 4 g cm^(-3)`
`4 = (2 xx M)/((500 xx 10^(-10))^(3) xx (6 xx 10^(23)))`
`M = (4 xx (500 xx 10^(-10))^(3) xx 6 xx 10^(23))/(2)`
`= 150 g mol^(-1)`