Density of a unit cell is represented as
`rho=("Effectiveno.ofatom(s)x Mass of a unit cell")/("Volume of a unit cell")=(Z.M.)/(N_(A).a^(3))`
Where, mass of unit cell = mass of effective no. of atom(s) or ion(s).
M = At. wt./formula wt.
`N_(A)="Avogadro’s no. "rArr 6.023xx10^(23)`
a = edge length of unit cell 
An element crystallizes in a structure having foc unit cell of an edge 200 pm. Calculate the density,if 100g this element contains `12 xx 10^(23)` atoms : 

Options

A. `41.66g//cm^(3)`
B. `4.166g//cm^(3)`
C. `10.25g//cm^(3)`
D. `1.025g//cm^(3)`

Answer

A

Explanation

`12 xx 10^(23)` atoms `to 100 gm, 6 xx 10^(23) to 50 gm`