`CsBr` crystallises in a body`-` centred cubic lattice. The unit cell length is `436.6 p m`. Given that `:` the atomic mass of `Cs=133` and that of `Br=80 am u` and Avogadro's number being `6.02xx10^(23)mol^(-1)`, the density of `CsBr` is `:`

Options

A. `8.25 g//cm^(3)`
B. `4.25 g//cm^(3)`
C. `42.5 g//cm^(3)`
D. `0.425 g//cm^(3)`

Answer

b

Explanation

`Z` for `CsBr = 1`
`( :.` one effective molecule is present) one is `Cs` atoms and one is `Br` atoms
`d= (ZM)/(N_(0) a^(3))`
`= (1 xx 213)/((4.366 xx 10^(-8))^(3) xx 6.02 xx 10^(23))`
`= 4.25 g//cm^(3)`