The density of `KBr` is `2.75 g cm^(-3)`. The length of the unit cell is `654` pm. Atomic mass of `K = 39, Br = 80`. Then what is true about the predicted nature of the solid?

Options

A. Unit cell is fcc
B. Z = 4
C. There are four constituents/unit cells
D. There are 8 ions at corners and 6 at the centres of the faces

Answer

A,B,C,D

Explanation

`z=(rho xx a^(3)xx10^(-30)xx N_(0))`
`=(2.75xx(654)^(3)xx10^(-30)xx6.02xx10^(23))/(119)=4`
As Z = 4, it is fcc unit cell. There are four KBr units. There are 8 ions at the comers and 6 at the face centres.
Hence (A), (B), (C ) and (D) are the the correct answers.